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First published online May 15, 2009
Journal of Experimental Biology 212, 1662-1671 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.028084
Review Article |
Carbonic anhydrases and anion transport in mosquito midgut pH regulation
The University of Florida Whitney Laboratory, 9505 Ocean Shore Boulevard, St Augustine, FL 32080, USA
* Author for correspondence (e-mail: pjl{at}whitney.ufl.edu)
Accepted 3 February 2009
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Summary |
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 TOP Summary IntroductionCarbonic anhydrase and midgut...Summary, conclusions and the...References |
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Key words: carbonic anhydrase, mosquito larva, alkalization, midgut, pH
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Introduction |
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TOPSummaryIntroductionCarbonic anhydrase and midgut...Summary, conclusions and the...References |
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). The relationship between mosquitoes, specific disease
organisms including viruses and various parasites, and human hosts is also
very highly evolved. Since the turn of the 20th century, malaria alone has
killed probably over 100 million people and infected billions.
Mosquitoes are holometabolous insects. This term describes the fact that
mosquitoes have distinct structural and physiological forms during the
development from zygote to reproductive adult. Among the four forms (embryo,
larva, pupa, imago) the two best recognized by the non-scientist are the
larval stage and the adult (imago). Adult female mosquitoes, because they are
the vectors of disease for many vertebrate animals, are a focus of control
strategies. These strategies are frequently targeted in some way to the
winged, flying adult and its behavior and habitats. Largely because adult
female mosquitoes are the vector of disease, much research focuses on analyses
of their biology. In reality, larval stage mosquitoes are much more abundant
than adults and quite distinct in form and function. Larval mosquitoes are
aquatic organisms and contrast dramatically with the blood or nectar consuming
adult form. In many ways, larval biology is very different from the adult. In
circumstances in which larval populations are readily located, larval control
strategies are very effective in population reduction (e.g.
Killeen et al., 2002). Never
the less, relatively little is known about larval biology as might be revealed
by modern, state-of-the art molecular physiological analyses. An in-depth
understanding of larval biology has the potential to provide new and
environmentally safe control strategies.
A specific aspect of larval mosquito biology that has the potential for
producing new directions in control and population management is food
ingestion, digestion and nutrient absorption. Larval insects spend the
majority of their time eating, with the digestive tract being a major portion
of the organism's body mass. Larval mosquitoes, similar to certain other
dipteran and lepidopteran larvae, utilize an initial digestive strategy that
is contrary to most other complex organisms on earth: the anterior portion of
the larval mosquito midgut (stomach) harbors a luminal pH as high as
10.5–11 (Fig. 1)
(Dadd, 1975;
Dow, 1984;
Zhuang et al., 1999). Most
other organisms utilize a gut luminal pH in the acidic range to initiate food
digestion. Aspects of how this pH is generated and related questions of food
digestion and ionic homeostasis in larval mosquitoes are the main subjects of
this review.
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;
Zhuang et al., 1999). At
approximately half the distance from the GC to the termination of the midgut,
the epithelial cells change character: the AMG cells (anterior half of the
midgut) are distinguished by an apical surface nearly devoid of membrane
expansions and/or microvilli; the PMG cells (posterior half of the midgut)
exhibit very elaborate amplifications of apical cell surface in the form of
vast arrays of microvilli (ibid.). The posterior end of the midgut transitions
into the hindgut through a region called the pylorus, followed by the ileum,
and then finally the rectum. At the anterior end of the pylorus, lateral
cellular tubules (Malpighian tubules) extend from the gut epithelium into the
surrounding hemolymph.
The roles of the various cell types within the gut are poorly understood.
In general, the GC cells are believed to be involved in the digestion and
absorption of proteins and carbohydrates, as well as the secretion of
antimicrobial peptides that help keep ingested organisms and pathogens under
control. The anterior midgut is devoted mainly to the digestion and absorption
of lipids, as well as the detoxification of dietary xenobiotics. The PMG is
involved in the metabolism and absorption of carbohydrates and proteins. The
Malpighian tubules are thought to be the main ion regulatory organs of the
mosquito, and are also involved in xenobiotic detoxification. The hindgut
apparently plays roles in the final steps of digestion, absorption,
elimination of waste, and retention of crucial ions
(Bradley, 1987;
Strange et al., 1982;
Wigglesworth, 1932). For a
more detailed description of the functional compartmentalization of the larval
gut, see the transcriptomic analysis recently published by Neira Oviedo et al.
(Neira Oviedo et al.,
2008).
In the midst of many concurrent events regulated by the cellular diversity
of the larval gut, a pH gradient of phenomenal proportions is established and
maintained without any physical barriers to the different pH zones. The pH in
the GC lumena and gut lumen at the region of the GC is 7.5–8
(Dadd, 1975;
Zhuang et al., 1999).
Immediately posterior to that is the AMG where the luminal pH rises rapidly to
10.5–11. In the PMG, the luminal pH drops to 7–8 again as in the
GC (Fig. 1). The pH in the
hindgut (specifically the rectum) drops again to 6.5–7.0
(Clark et al., 2007) (K.E.S.,
unpublished observations).
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Carbonic anhydrase and midgut pH |
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;
Wieczorek, 1992). In this
organism, the luminal pH can reach 12 (ibid.). The transepithelial potential,
which, along with epithelial transport processes, supports a luminal pH of 12
and a blood/hemolymph pH of near 7 has been intensely studied in this organism
with some remarkable insights (ibid.) (see also
Harvey, 2009). The actual
buffer at such an extremely alkaline pH is very likely to be carbonate
(CO32–) and paired with a strong cation such as
K+ or Na+ (Dadd,
1975; Dow, 1984).
Indeed, the logical source of the CO32– is
metabolic CO2 and its ionization through the activity of the enzyme
carbonic anhydrase (CA). The reaction can be simply represented:
CO2+H2O
HCO3–+H+.
Deprotonization of the bicarbonate ion would then produce
CO32– which has a pKa of
approximately 10.3. Thus, it seems probable that one or more CAs would be
present and involved in the alkalization of the caterpillar gut. In the late
1990s, interest in alkalization mechanisms of the larval mosquito gut rose as
a result of the possibility that this biological system might be amenable to
the development of new larval control strategies.
Confirmation of CA as a central element of the larval mosquito midgut
alkalization system came with the demonstration that H+ and
Cl– flux across the midgut epithelium of Aedes
aegypti was CA dependent (Boudko et
al., 2001). Using SERIS-LIX (self-referencing ion-selective liquid
ion exchanger) microelectrodes in a vibrating mode, ionic fluxes from the
basal surface of the midgut were measured as a function of position along the
anterior–posterior axis. The net vectorial flux of both H+
and Cl– showed remarkable polarity reversal along the length
of the midgut, in rough correlation with the pH gradient in the lumen of the
tube. When CA inhibitors were applied, flux of H+ and
Cl– ions was dramatically reduced or eliminated
(Boudko et al., 2001)
indicating that CA activity was central to ion fluxes that are likely to be
central to pH regulation in the midgut.
In 2002, the first characterization of a specific CA from a mosquito
(larval Aedes aegypti) was published by Corena et al.
(Corena et al., 2002).
Traditional biochemical and enzymatic methodologies showed that the
accumulation of base in the aquatic environment of the living larvae was
sensitive to classic inhibitors of the 
-CA family, such as
methazolamide and acetazolamide (Corena et
al., 2002). However, CA inhibition led to a neutralization of the
highly alkaline regions of the midgut lumen. This work was performed before
the publication of any mosquito genomes and hence a mosquito CA cDNA
homology-cloning strategy was pursued based on sequences from several
vertebrate CAs and putative CAs from the Drosophila melanogaster EST
database. Corena et al. (Corena et al.,
2002) published the first complete sequence of any insect CA from
the yellow fever mosquito, Aedes aegypti. Sequence alignments and
homology analyses showed this mosquito CA to be an -CA possessing key
elements of the classic active site including the three definitive histidine
residues used in the GO (gene ontology;
http://www.geneontology.org)
database as a defining characteristic.
The tissue distribution of the first CA characterized from an insect turned
out to be a bit of a surprise. -CAs of vertebrate systems have been
identified that can be located in one of five different compartments,
reflected by gene, transcript and protein structure: soluble cytoplasmic CAs,
integral transmembrane CAs, secreted soluble CAs, mitochondrial CAs,
peripheral GPI-linked membrane CAs
(Hewett-Emmett and Tashian,
1996). The newly cloned CA from Aedes aegypti was shown
to be of the final type, a GPI-linked peripheral membrane protein
(Seron et al., 2004).
Publication of the genome of a species of mosquito, Anophleles
gambiae (Holt et al.,
2002), provided the material for `in silico' analyses which
confirmed the presence of an orthologous CA in Anophleles with the
characteristic signal peptide of secreted GPI-linked proteins
(Seron et al., 2004). A
polyclonal antiserum to a peptide sequence unique to this CA, but conserved
between the two orthologous mosquito CAs, was used to confirm a cell surface
location. Surprisingly, the localization studies showed this CA to be
predominantly present on the basal membranes of a specific subset of midgut
muscles (Fig. 2). It is well
known that the midgut of mosquito larvae (and most probably all larval
insects) is invested with a tubular arrangement of striated muscle fiber
bundles that extend both longitudinally and circumferentially along the basal
aspect of the gut tubular epithelium (e.g.
Jones, 1960). These muscles
are hypothetically involved in the movement of food through the length of the
gut tube via peristaltic and antistaltic waves of contraction
(Jones, 1960). Immunolabeling
for the mosquito CA showed it to be on the muscle cell surface
(Seron at al., 2004). It also
demonstrated that the musculature of the gut had at least two distinguishable
sub-domains beyond the recognized division into longitudinal and
circumferential. CA immunostaining and confocal microscopy showed that on the
lateral sides of the gut tube, a subset of muscles were labeled, whereas other
muscles that overlapped with these on the lateral sides and those running
purely on dorsal and ventral sides did not possess the CA
(Fig. 2). The physiological
implications of this localization pattern and the newly identified complexity
of muscle distribution in the midgut remain purely a matter for speculation at
this point. The character of this specific CA was analyzed by molecular
cloning with the signal/GPI linkage sequence removed. The expressed protein
exhibited high activity characteristics similar to the high activity human
form CAII (Fisher et al.,
2006). Attempts to crystallize the protein were unsuccessful but
in silico comparisons predict a three-dimensional structure very similar to
that of human and mammalian CAs with known structures (ibid.).
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-CA and one β-CA gene sequences. β-CAs are from a different
evolutionary origin than the -CAs and are more commonly found in
prokaryotes (Hewett-Emmett and Tashian,
1996). The presence of a β-CA gene in the mosquito genome is
very interesting but as yet CA enzymatic activity has not been demonstrated
for this mosquito gene product. Table
1 lists each of these 12 predicted CAs with assigned nomenclature
(Smith et al., 2007).
Fig. 3 shows a molecular
phylogenetic analysis of CA genes from three genomic model insects
[Drosophila melanogaster (red); Anopheles gambiae (green);
Aedes aegypti (blue); and human (black)]. Several observations can be
made from the phyolgenetic/genome sequence analyses. First, the majority of
insect CAs cluster separately from the human CAs. This probably indicates that
gene duplications that led to the range of 12 mosquito CAs and 16 human CAs
occurred primarily after the divergence of protostomes and deuterostomes.
There are a few notable exceptions to this. Both of the mosquito and the fruit
fly genomes possess two CA-related genes that cluster with two human
CA-related genes. These genes have been termed CA-RPs (CA-related proteins) in
the vertebrate literature (Tashian et al.,
2000). They are clearly evolved from an -CA ancestral gene
by virtue of numerous sequence similarities but are in fact not active CA
enzymes as they all lack one or more of the crucial active site histidine
residues (ibid.). The CA-RPs are very well conserved in vertebrate evolution
(ibid.) and the insect analyses show that this conservation goes back even
further to a common ancestor to the protostomes and deuterostomes. The
function of these conserved gene products remains unresolved.
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The third -CA of the mosquito that shows an evolutionary
relationship with some human CAs is AgCA9 [orthologous to Aedes
aegypti Ae4930PA and Drosophila melanogaster CG7820PA (Ensemble
designations)]. AgCA9 clusters with several human CAs including CAVII which is
considered to be the human CA most similar to an ancestral gene of origin
(Hewett-Emmett and Tashian,
1996). Clustering of three orthologous insect genes with human
CAVII is consistent with the hypothesis that this insect CA is also relatively
close to the evolutionary origins of the -CA gene family
(Smith et al., 2007). The cDNA
for the mRNA of AgCA9 was cloned and its expression analyzed (ibid.).
Quantitative PCR, microarray and in situ hybridization analyses
showed the message to be differentially expressed in the various regions of
the larval midgut with highest levels of expression in the GC and the rectum
(Smith et al., 2007;
Neira Oviedo et al., 2008). To
examine the distribution of the actual enzyme in an effort to see if it might
play a role in gut alkalization and ion homeostasis, a polyclonal antibody was
prepared to a specific unique amino acid sequence of AgCA9 and was used to
determine the protein distribution using immunohistochemistry and confocal
microscopy (ibid.) (Smith et al.,
2008). Fig. 4 shows
a summary of the localization studies. In longitudinal paraffin sections of
fourth instar larvae, immunofluorescence for AgCA9 is evident in several key
locations. First, AgCA9 immunoreactivity is evident in the cells and lumen of
the GC. There is also an apparent robust accumulation of the antigen in the
ectoperitrophic space (ectoperitrophic fluid) which stands between the PT and
the cells of the gut epithelium. Another location of strong expression is in
specific cells of the rectum. Malpighian tubules (MTs) also show AgCA9
immunoreactivity in the so-called principal cells
(Smith et al., 2007).
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5-subunit of Na+K+-ATPase
(Smith et al., 2007;
Okech et al., 2008). The
striking observation made was that the two proteins are expressed in mutual
exclusion in two subsets of the rectum epithelium. AgCA9 is found only in a
dorsal, anterior grouping of rectum cells (termed DAR cells) and the ATPase is
found exclusively in the remaining AgCA9-negative epithelial cells.
Fig. 4D shows a longitudinal
section at high magnification, again showing AgCA9 in DAR cells (green) and
Na+K+-ATPase (red) in all other rectal epithelial cells
(non-DAR cells). Fig. 4E shows
a whole-mount in which DAR cells (AgCA9; green) and the basal surface
musculature of the rectum is labeled with TRITC-phalloidin (red). These
analyses demonstrated a functional differentiation between specific cell types
of the anopheline rectum that had not previously been described
(Smith et al., 2007).
Ion regulation in mosquito larvae can be a very dynamic function in
survival. Many types of mosquito larvae thrive in aquatic environments that
can vary greatly in many parameters including pH, osmolarity and ionic milieu.
Through the course of larval development, such events as rainfall or
evaporation can dramatically change the nature of the osmotic environment. To
cope with such changes, mosquito larvae need to adapt to these changes. The
rectum is one of the key organs in controlling the final composition of the
mosquitoes excretions and hence the composition of the hemolymph. In species
of Anopheline mosquitoes that can tolerate wide swings in the osmotic strength
of their habitats, protein distribution adjustments take place
(Smith et al., 2008).
Anopheles albimanus, as a specific example, is a salt-tolerant
mosquito species. When raised in freshwater, the distribution of AgCA9 and
Na+K+-ATPase are as described above for Anopheles
gambiae (see Fig. 4). If,
by contrast, the same species is raised in 50% sea water, the
Na+K+-ATPase primary location shifts from the non-DAR
cells into the DAR cells (Smith et al.,
2008). The specific physiological implications of shifting the
ATPase activity from cells lacking AgCA9 to those that possess the CA is under
active investigation but unclear at the time of writing. It seems probable
that other enzymes and transporters that play roles in ionic absorption or
excretion are also impacted by altering the aquatic environment of the larvae.
The full range of important biological systems in this context remains to be
studied.
The detection of a soluble CA in the ectoperitrophic space of the gut was
unexpected and has implications in the regulation of gut luminal pH. The
sequence of AgCA9 has no apparent signal peptide that would be indicative of a
secreted protein. CAVI, the human/mammalian salivary CA does indeed possess
such a characteristic sequence (Tashian et
al., 2000). Certainly, the absence of a signal peptide does not
preclude certain types of secretion, such as merocrine exocytosis in insects
(Hung et al., 2000). The
presence of a soluble CA in the ectoperitrophic space may be central to the pH
alkalization paradigm. The presence of high transepithelial potentials and
numerous mitochondria in the gut epithelial cells
(Harvey, 1992;
Wieczorek, 1992) are both
indicative of very high metabolic activity in these cells. Under normal
aerobic conditions the final product of such activity will be CO2.
In large, complex organs, metabolic CO2 is typically converted to
carbonic acid and/or bicarbonate intracellularly, which is then transported in
a vectorial fashion by an anion exchanger such as AE1 (in human) out of the
cell (Romero et al., 2004). In
a very small tissue such as a single-cell epithelial tube, the diffusion of
gaseous CO2 into an extracellular environment containing high
concentrations of a soluble CA, which would rapidly ionize the catabolite,
might obviate the need for specific anion exchange/transport mechanisms.
Nevertheless, the mosquito genome does indeed encode proteins whose motif and
homology analyses have lead to annotation as putative anion exchangers of the
type frequently found in association with CA-containing tissues and cells.
Fig. 5 shows a summary
analysis of putative members of the SLC4A family of anion exchangers in the
mosquito genome. Three distinct gene sequences of the Anopheles
gambiae genome have been annotated as members of this family of anion
exchangers [AY280611, EU068741 (GenBank) and AGAP006968 (Ensembl)] with one
gene predicted to exist as at least two distinct splice variants. There is
evidence (M.N.O., unpublished observations) that several splice variants exist
in the mRNA pool from gut samples. The predicted transcripts show a high
degree of homology with the single insect anion exchanger characterized to
date, so-called NDAE1 from Drosophila melanogaster
(Romero et al., 2000;
Sciortino et al., 2001). The
Aedes aegypti genome contains at least two genes with additional
splice variants predicted. Multiple potential splice variants also muddle the
analysis of related genes in Drosophila melanogaster as well
(Fig. 5).
Fig. 5 also shows a hydropathy
map analysis of the Anopheles gambiae gene AgAE1 compared
with that of Ndae1 from Drosophila melanogaster. The
structural homology between the two is obvious. This figure also shows a
two-dimensional model of the amino acid sequence depicting a hypothetical
structure very similar to that of other examples of
Cl–/HCO3– exchangers (e.g.
Romero et al., 2000;
Romero et al., 2004). Cloning
of a full-length cDNA of the gene annotated as AgAE1 has been
problematic and we have evidence of numerous splice variants of this anion
exchanger. The carboxyl terminus cytoplasmic tail of AgAE1 is highly variable
in cloning analyses and the sequence shown is only one of several that have
emerged in separate cloning efforts (T.J.S. and M.N.O., unpublished
observations). Work in progress will hopefully provide both physiological
characterization as well as immunolocalization of this potentially important
element of acid–base regulation in the larval mosquito gut. Recent
microarray-based transcriptome analyses
(Neira Oviedo et al., 2008)
indicate that at least two out of the three annotated anion exchanger genes in
Anopheles gambiae larvae exhibit differential expression in the
regions of the gut. Fig. 6
shows microarray data for all three of the specific AE-type genes. In this
analysis, RNA isolated from dissected regions of the gut (GC, AMG, PMG and HG)
was compared to whole gut (W) using Affymetrix microarray
(Neira Oviedo et al., 2008).
The two AE genes designated as AE1 (AgAE1 in
Fig. 5) and AE2 (AgAE2
in Fig. 5) showed enrichment in
specific gut regions relative to the whole gut sample. AgAE1 was
enriched in the HG sample (which includes the rectum and MT, which are
locations of CA9) whereas AgAE2 showed enrichment in the GC
sample (an additional site of AgCA9 expression). Although
AgAE3 showed no specific enrichment in gut regions, it is not safe to
interpret the data as indicating that the gene is not expressed in the gut. By
the `present' versus `absent' analysis generated by the Affymetrix
methodology, AE3 is `absent' from the gut and thus seems to be more
abundant in tissues other than the gut
(Neira Oviedo et al., 2008).
Early physiological analyses indicated that gut alkalization in the mosquito
larva is affected by the generalized pharmacological blocker of anion
exchangers DIDS (Boudko et al.,
2001; Corena et al.,
2004). It remains to be seen whether any of the predicted members
of the AE gene family in mosquitoes are specifically involved in pH regulation
in any or all regions of the larval alimentary canal.
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Another family of solute carriers, the SLC26 gene family [multifunctional
anion exchangers (e.g. Mount and Romero,
2004)] has potentially important roles in pH balance and anion
transport. Indeed, the Anopheles gambiae genome has annotated three
members of this specific gene family [AGAP010344, AGAP010389 and AGAP010725
(Ensembl)]. Transcripts levels of all three of these genes show differential
enrichment when queried against the larval alimentary canal microarray
expression profile (Neira Oviedo et al.,
2008). Transcripts levels of both AGAP010389 and AGAP010344 are
enriched in the hindgut relative to other gut regions, relative to the
salivary glands (our unpublished observations) and relative to the whole
insect (Neira Oviedo et al.,
2008). The transcript level of AGAP010725 is enriched in the
salivary glands (our unpublished observations) and the GC
(Neira Oviedo et al., 2008).
Little is known about this family of SLCs in mosquitoes and we are actively
pursuing their characterization.
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Summary, conclusions and the road ahead |
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-CAs (AgCA9 and AgCA10) indicated.
Although it is clear that CA activity is central to pH regulation in the gut,
it is presumed that these two specific CAs play important roles. We know that
other CAs are present in the gut but their distribution and specific roles
(and the roles of already characterized CAs) remain to be elucidated. The
bottom half of Fig. 7 shows the
distributions of a few of the known enzymes and transporters that probably
play important roles in gut pH regulation. Four stylized cells are shown: GC,
AMG, PMG and muscle. The differential distribution of key proteins such as
V-ATPase (V), Na+/K+-ATPase (Na/K) and the
Na+/H+ antiporter (NHA) energize the transepithelial
potential and provide the driving force for producing extreme pH gradients
along the length of the gut (Harvey,
1992; Wieczorek,
1992; Harvey et al., 2009). CA activity rapidly converts metabolic
CO2 into ionic forms that are then vital to buffering the pH ranges
of the gut lumen. CAs exist within specific cell types of the gut as well as
in extracellular compartments. This wide range of distribution is indicative
of the important role that CA plays at all stages of ion and pH regulation in
the larval mosquito gut. It should be noted that a recent review
(Onken and Moffett, 2009)
compared analyses described herein with analyses of the Aedes aegypti
isolated gut preparation. In this preparation, the anterior portion of the gut
tube (i.e. the AMG) was isolated from other organismal elements such as
luminal contents, PT, ectoperitrophic fluid and all of the upstream and
downstream contributions from other regions of the alimentary canal. The
authors discuss both published and `unpublished' data that infers that
isolated AMG can continue to alkalize the gut lumen even in the presence of CA
inhibition. The role of a soluble CA in the ectoperitrophic fluid is brought
into question. But in this simplified system (i.e. the perfused AMG) it seems
probable that the continued presence of a vectorial capacity to move
H+ ions from the apical luminal side to the basal hemolymph side
could alkalize the lumen with no apparent need for locally produced
HCO3–. A basally located V-ATPase
(Harvey 1992,
Zhuang et al., 1999) and an
apical exchange mechanism for cations could produce measurable alkalization of
the AMG lumen. Also, the assumed effectiveness of pharmacological inhibitors
that have never been well characterized in mosquito systems creates concern.
As Onken and Moffett (Onken and Moffett,
2009) state, more is probably unknown than known about this system
with many avenues to pursue. Perhaps, until potency and specificity of these
pharmacological agents have been demonstrated in the mosquito system, the
pursuit of a clear model will be aided by further molecular (genetic and
proteomic) characterization of known and potential effectors in this complex
biological system. Among our several goals and ongoing investigations is the
application of reverse genetic techniques to query the roles of specific gene
products in pH and ion balance in the alkaline midgut of the mosquito
larva.
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Footnotes |
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References |
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TOPSummaryIntroductionCarbonic anhydrase and midgut...Summary, conclusions and the...References |
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Black, W. C. and Kondratieff, B. C. (2005). Evolution of arthropod disease vectors. In Biology of Disease Vectors, 2nd edn (ed. W. C. Marquardt), pp.9 -23. Burlington, MA: Elsevier.
Boudko, D. Y., Moroz, L. L., Harvey, W. R. and Linser, P. J.
(2001). Alkalinization by chloride/bicarbonate pathway in larval
mosquito midgut. Proc. Natl. Acad. Sci. USA
98,15354
-15359.
Bradley, T. J. (1987). Physiology of osmoregulation in mosquitoes. Annu. Rev. Entomol. 32,439 -462.[Medline]
Clark, T. M., Vieira, M. A., Huegel, K. L., Flury, D. and
Carper, M. (2007). Strategies for regulation of hemolymph pH
in acidic and alkaline water by the larval mosquito Aedes aegypti
(L.) (Diptera;Culicidae). J. Exp. Biol.
210,4359
-4367.
Clements, A. N. (1992). The Biology of Mosquitoes, vol. 1 (ed. A. N. Clements). London: Chapman Hall.
Corena, M. P., Seron, T. J., Lehman, H. K., Ochrietor, J. D.,
Kohn, A., Tu, C. and Linser, P. J. (2002). Carbonic anhydrase
in the midgut of larval Aedes aegypti: cloning, localization and
inhibition. J. Exp. Biol.
205,591
-602.
Corena, M. P., Fiedler, M. M., VanEkeris, L. and Linser, P. J. (2004). A comparative study of carbonic anhydrase in the midgut of mosquito larvae. Comp. Biochem. Physiol. 137,207 -225.
Dadd, R. H. (1975). Alkalinity within the midgut of mosquito larvae with alkaline-active digestive enzymes. J. Insect Physiol. 46,1847 -1853.
Dow, J. A. T. (1984). Extremelu high pH in the biological systems: a model for carbonate transport. Am. J. Physiol. 246,R633 -R635.[Medline]
Fisher, S. Z., Tariku, I., Case, N. M., Tu, C., Seron, T., Silverman, D. N., Linser, P. J. and McKenna, R. (2006). Expression, purification, kinetic, and structural characterization of an alpha-class carbonic anhydrase from Aedes aegypti (AaCA1). Biochim. Biophys. Acta 1764,1413 -1419.[Medline]
Harvey, W. R. (1992). Physiology of V-ATPases.
J. Exp. Biol. 172,1
-17.
Harvey, W. R. (2009). Voltage coupling of
primary H+ V-ATPases to secondary Na+- or
K+-dependent transporters. J. Exp. Biol.
212,1620
-1629.
Hewett-Emmett, D. and Tashian, R. E. (1996). Functional diversity, conservation and convergence in the evolution of the alpha-, beta- and gamma-carbonic anhydrase gene families. Mol. Phylogenet. Evol. 5,50 -77.[CrossRef][Medline]
Holt, R. A., Subramanian, G. M., Halpern, A., Sutton, G. G.,
Charlab, R., Nusskern, D. R., Wincker, P., Clark, A. G., Ribeiro, J. M.,
Wides, R. et al. (2002). The genome sequence of the malaria
mosquito Anopheles gambiae. Science
298,129
-149.
Hung, C., Lin, T. and Lee, W. (2000). Morphology and ultrastructure of the alimentary canal of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera:Tephritidae)(2): The structure of the midgut. Zool. Stud. 39,387 -394.
Jones, J. C. (1960). The anatomy and rhythmical activities of the alimentary canal of Anopheles larvae. Ann. Entomol. Soc. Am. 53,459 -474.
Killeen, G. F., Fillinger, U. and Knols, B. G. J. (2002). Advantages of larval control for African malaria vectors: low mobility and behavioural responsiveness of immature mosquito stages allow high effective coverage. Malar. J. 1, 8.[CrossRef][Medline]
Mount, D. B. and Romero, M. F. (2004). The SLC26 gene family of multifunctional anion exchangers. Pflugers Arch. 447,710 -721.[CrossRef][Medline]
Neira Oviedo, M., VanEkeris, L., Corena-Mcleod, M. D. and Linser, P. J. (2008). A microarray-based analysis of transcriptional compartmentalization in the alimentary canal of Anopheles gambiae (Diptera: Culicidae) larvae. J. Insect. Mol. Biol. 17,61 -72.
Okech, B. A., Boudko, D. Y., Linser, P. J. and Harvey, W. R.
(2008). Cationic pathway of pH regulation in larvae of
Anopheles gambiae. J. Exp. Biol.
211,957
-968.
Onken, H. and Moffett, D. F. (2009). Revisiting
the cellular mechanisms of strong luminal alkalinization in the anterior
midgut of larval mosquitoes. J. Exp. Biol.
212,373
-377.
Romero, M. F., Henry, D., Nelson, S., Harte, P. J. and
Sciortino, C. M. (2000). Cloning and characterization of a
Na+ driven anion exchanger (NDAE1): a new CNS bicarbonate
transporter. J. Biol. Chem.
275,24552
-24559.
Romero, M. F., Fulton, C. M. and Boron, W. F. (2004). The SLC4 family of HCO3– transporters. Eur. J. Physiol. 204,495 -509.
Sciortino, C. M., Shrode, L. D., Fletcher, B. R., Harte, P. J. and Romero, M. F. (2001). Localization of endogenous and recombinant Na+-driven anion exchanger protein NDAE1 from Drosophila melanogaster. Am. J. Physiol. Cell Physiol. 281,449 -463.
Seron, T. J., Hill, J. and Linser, P. J.
(2004). A GPI-linked carbonic anhydrase expressed in the larval
mosquito midgut. J. Exp. Biol.
207,4559
-4572.
Smith, K. E., VanEkeris, L. A. and Linser, P. J.
(2007). Cloning and characterization of AgCA9, a novel
-carbonic anhydrase from Anopheles gambiae Giles sensu stricto
larvae. J. Exp. Biol.
210,3919
-3930.
Smith, K. E., VanEkeris, L. A., Okech, B. A., Harvey, W. R. and
Linser, P. J. (2008). Larval anophleine mosquito recta
exhibit a dramatic change in localization patterns of ion transport proteins
in response to shifting salinity: a comparison between anopheline and culicine
larvae. J. Exp. Biol.
211,3067
-3076.
Strange, K., Phillips, J. E. and Quamme, G. A. (1982). Active HCO3– secretion in the rectal salt gland of a mosquito larva inhabiting NaHCO3-CO3 lakes. J. Exp. Bol. 101,171 -186.
Tashian, R. E., Hewett-Emmett, D., Carter, N. D. and Bergenhem, N. C. (2000). Carbonic anhydrase (CA)-related proteins (CA-RPs), and transmembrane proteins with CA of CA-RP domains. In The Carbonic Anhydrases: New Horizons (ed. W. R. Chegwidden, N. D. Carter and Y. H. Edwards), pp.105 -120. Basel: Birkhäuser.
Wieczorek, H. (1992). The insect V-ATPase, a
plasma membrane proton pump energizing secondary active transport: molecular
analysis of electrogenic potassium transport in the tobacco hornworm midgut.
J. Exp. Biol. 172,335
-344.
Wigglesworth, V. B. (1932). On the function of the so called "rectal glands" of insects. J. Cell Sci. 75,131 -150.
Zhuang, Z., Linser, P. J. and Harvey, W. R. (1999). Antibody to H+ V-ATPase subunit E colocalizes with portasomes in alkaline larval midgut of a freshwater mosquito (Aedes aegypti). J. Exp. Biol. 202,2449 -2460.[Abstract]
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