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

EMBO J. 1996 Aug 15;15(16):4100-10.

Abstract

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.

MeSH terms

  • Animals
  • Barium / metabolism
  • Biological Transport
  • Calcium Channels / classification
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • DNA, Complementary / genetics
  • Macromolecular Substances
  • Membrane Potentials
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Nerve Tissue Proteins / metabolism*
  • Oocytes / metabolism
  • Qa-SNARE Proteins
  • RNA, Complementary / metabolism
  • Synaptosomal-Associated Protein 25
  • Xenopus laevis

Substances

  • Calcium Channels
  • DNA, Complementary
  • Macromolecular Substances
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Qa-SNARE Proteins
  • RNA, Complementary
  • Synaptosomal-Associated Protein 25
  • Barium