Functional interaction of syntaxin and SNAP-25 with voltage-sensitive L- and N-type Ca2+ channels.
We have used an electrophysiological assay to investigate the functional interaction of syntaxin 1A and SNAP-25 with the class C, L-type, and the class B, N-type, voltage-sensitive calcium channels. Co-expression of syntaxin 1A with the pore-forming subunits of the L- and N-type channels in Xenopus oocytes generates a dramatic inhibition of inward currents (>60%) and modifies the rate of inactivation (tau) and steady-state voltage dependence of inactivation. Syntaxin 1-267, which lacks the transmembrane region (TMR), and syntaxin 2 do not modify channel properties, suggesting that the syntaxin 1A interaction site resides predominantly in the TMR. Co-expression of SNAP-25 significantly modifies the gating properties of L- and N-type channels and displays modest inhibition of current amplitude. Syntaxin 1A and SNAP-25 combined restore the syntaxin-inhibited N-type inward current but not the reduced rate of inactivation. Hence, a distinct interaction of a putative syntaxin 1A-SNAP-25 complex with the channel is apparent, consistent with the formation of a synaptosomal SNAP receptors (SNAREs) complex. The in vivo functional reconstitution: (i) establishes the proximity of the SNAREs to calcium channels; (ii) provides new insight into a potential regulatory role for the two SNAREs in controlling calcium influx through N- and L-type channels; and (iii) may suggest a pivotal role for calcium channels in the secretion process.
Wiser
O
O
Department of Biological Chemistry, The Hebrew University of Jerusalem, Israel.
Bennett
M K
MK
Atlas
D
D
D000818:Animals; D001464:Barium / Q000378:metabolism; D001692:Biological Transport; D015220:Calcium Channels / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D046911:Macromolecular Substances; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D050765:Qa-SNARE Proteins; D018075:RNA, Complementary / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25; D014982:Xenopus laevis
D015220:Calcium Channels; D018076:DNA, Complementary; D046911:Macromolecular Substances; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D018075:RNA, Complementary; D050825:Synaptosomal-Associated Protein 25; D001464:Barium