Lotan, I. | Search bioRxiv

bioRxiv2026

Gβγ dually regulates the M current via increased channel surface expression and PIP2 sensitivity

The M-current, generated by voltage gated KV7.2/7.3 channels, sets the threshold for neuronal action potential and acts as a key brake on repetitive firing. The M-current is tightly regulated by signaling molecules, such as calmodulin and phosphatidylinositol-4,5-bisphosphate (PIP2). Here, we show that coexpression of the ubiquitous subunit dimer of heterotrimeric G-proteins, G{beta}{gamma}, with KV7.2/7.3 in Xenopus laevis oocytes doubles maximal M-current. This regulation requires free, prenylated, membrane-associated G{beta}{gamma} and operates via two distinct mechanisms: 1) increasing plasma membrane (PM) channel density and 2) stabilizing KV7.2/7.3-PIP2 coupling. Conversely, G{beta}{gamma} scavengers reduce basal KV7.2/7.3 current and weaken PIP2 coupling. Proximity ligation assays confirm colocalization of G{beta}{gamma} and KV7.2/7.3 in the PM. Peptide array and AlphaFold modeling identify putative interaction sites on the channel cytoplasmic domain. Finally, the disease-causing G{beta}1 variant I80N abolished G{beta}{gamma}-induced M-current potentiation. Together, these findings establish G{beta}{gamma} as a significant physiological regulator and potential site of vulnerability in neuronal M-current function.

physiology↗

bioRxiv2020

CK2 Phosphorylation is required for Regulation of Syntaxin 1A activity in Ca2+-triggered release in neuroendocrine cells

The polybasic juxtamembrane region (5RK) of the plasma membrane neuronal SNARE, syntaxin1A (Syx), was shown by us to act as a fusion clamp in PC12 cells, making release dependent on stimulation by Ca2+. By using a Syx-based FRET probe, we demonstrated that 5RK is absolutely required for a depolarization-induced Ca+2-dependent, close-to-open transition (CDO) of Syx that involves the vesicular SNARE synaptobrevin2 and occurs concomitantly with Ca2+-triggered release. Here, we investigated the mechanism underlying the 5RK requirement, and identified phosphorylation of Syx at Ser-14 (S14) by protein kinase CK2 as a crucial molecular determinant. Following biochemical verification that both endogenous Syx and CSYS are constitutively S14 phosphorylated in PC12 cells, dynamic FRET analysis of phospho-null and phospho-mimetic mutants of CSYS and the use of a CK2 inhibitor revealed that it is the S14 phosphorylation that confers the 5RK requirement. Concomitant amperometric analysis of catecholamine release revealed that the phospho-null mutants do not support release, spontaneous and evoked. Collectively, these results identify a functionally important CK2 phosphorylation site in Syx that is required for 5RK-regulation of CDO and for concomitant Ca2+-triggered release. Summary statementMany phospho-proteins participate in vesicle exocytosis. We show that a recently identified structural transition of syntaxin1A that accompanies Ca2+-regulated exocytosis in neuroendocrine cells is controlled by CK2 phosphorylation of syntaxin1A.

neuroscience↗