Fig. 4. Functional expression of PpCaVß. (A)
Current/voltage relationships of currents gated by CyCaV
in the presence (triangles) and absence (squares) of
PpCaVß. Values are means ± s.d. of from 13
(triangles) to 16 (squares) trials. (B) Peak amplitude (± s.d.) of
currents gated by CyCaV in the presence (black bar;
N=13) and absence (white bar; N=16) of
PpCaVß. In the presence of
PpCaVß, currents are significantly larger
(P<2x10-6). (C) Same, for currents gated by
CaV2.3 in the presence (dark bar; N=14) and absence (white
bar; N=14) of PpCaVß. In the presence of
PpCaVß currents are significantly larger
(P<0.012). (D) Current/voltage relationship of normalized currents
(± s.d.) gated by CyCaV in the presence (triangles;
N=13) and absence (squares; N=16) of
PpCaVß. Co-expression with
PpCaVß results in an obvious negative shift in the
I/V relationship. (E) The same, for currents gated by CaV2.3 in the
presence (triangles; N=16) and absence (squares; N=14) of
PpCaVß. The I/V relationship of
CaV2.3 is altered slightly by co-expression with
PpCaVß. Data points in D and E are fitted by the
Boltzman function
Inorn=gnorm(V-Vrev)/(1+exp[-(V-V
)]/k,
where g=conductance, Vrev=53.44, 63.4, 66.25 and
68.94, V=9.68, -0.5652, -3.067 and -7.281 and
k=9.443, 7.152, 7.357, and 6.163 for CyCaV,
CyCaV/PpCaVß, CaV2.3
and CaV2.3/PpCaVß. (F) The relationship
between time constant of inactivation of currents in the presence (triangles;
N=14) and absence (squares; N=9) of
PpCaVß. The time constant of inactivation was
determined by fits of exponential curves to the decay phase of the current. At
+10 mV, the time constant of inactivation of the current is significantly
faster (P>0.0015) in the presence of
PpCaVß. (G) Same, for currents gated by
CaV2.3. There was no significant difference in the rate of
inactivation under the two conditions.