Functional interaction of syntaxin and SNAP-25 with voltage-sensitive L- and N-type Ca2+ channels.

AUTOR(ES)

Wiser, O

RESUMO

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.

Documentos Relacionados

• L- and N-type Ca2+ channels in adult rat carotid body chemoreceptor type I cells.
• Molecular determinants of the functional interaction between syntaxin and N-type Ca2+ channel gating
• Functional dependence of Ca(2+)-activated K+ current on L- and N-type Ca2+ channels: differences between chicken sympathetic and parasympathetic neurons suggest different regulatory mechanisms.
• Role of L- and N-type Ca2+ channels in muscarinic receptor-mediated facilitation of ACh and noradrenaline release in the rat urinary bladder.
• Evidence for a voltage-dependent enhancement of neurotransmitter release mediated via the synaptic protein interaction site of N-type Ca2+ channels