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Received for publication July 26, 2004.
Revised October 27, 2004.
Accepted for publication October 27, 2004.
Kv2.1, the prevalent delayed-rectifier K+ channel in neuroendocrine and endocrine cells, was previously suggested by our group to be modulated in islet 
-cells by syntaxin 1A (Syx) and SNAP-25 (SNAP). We also demonstrated physical interactions in neuroendocrine cells between Kv2.1, Syx and SNAP-25, characterized their effects on Kv2.1 activation and inactivation in Xenopus oocytes, and suggested that they pertain to the assembly/disassembly of the Syx/SNAP-25 (t-SNARE) complex. In the present work we established the existence of a causal relationship between the physical and the functional interactions of Syx with the Kv2.1 channel, using three different peptides that compete with the channel for binding of Syx when injected into oocytes already co-expressing Syx with Kv2.1 in the plasma membrane. One peptide corresponding to the Syx-binding region on the N-type Ca2+ channel and two peptides corresponding to Syx-binding regions on the Kv2.1 C-terminus. All peptides reversed the effects of Syx on Kv2.1, suggesting that the hyperpolarizing shifts of the steady-state inactivation and activation of Kv2.1 caused by Syx result from cell-surface protein-protein interactions and point to participation of the C-terminus in such interaction. In line with these findings, the effects of Syx were dissipated by partial deletions of the C-terminus. Furthermore, the t-SNARE complex was shown here to bind to the Kv2.1 C-terminus, and its effects on the inactivation of Kv2.1 were dissipated by partial deletions of the C-terminus. Taken together, these findings suggest that physical interactions of both Syx and the t-SNARE complex with the C-terminus of Kv2.1 are involved in channel regulation.
Key words:
Ion channel regulation, Func. analysis receptor/ion channel mutants
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