G protein β subunits regulate Ca v 3.3 T-type channel activity and current kinetics via interaction with the Ca v 3.3 C-terminus.

Ca ²⁺ influx through Ca _v 3.3 T-type channel plays crucial roles in neuronal excitability and is subject to regulation by various signaling molecules. However, our understanding of the partners of Ca _v 3.3 and the related regulatory pathways remains largely limited. To address this quest, we employed the rat Ca _v 3.3 C-terminus as bait in yeast-two-hybrid screenings of a cDNA library, identifying rat Gβ ₂ as an interaction partner. Subsequent assays revealed that the interaction of Gβ ₂ subunit was specific to the Ca _v 3.3 C-terminus. Through systematic dissection of the C-terminus, we pinpointed a 22 amino acid sequence (amino acids 1789-1810) as the Gβ ₂ interaction site. Coexpression studies of rat Ca _v 3.3 with various Gβγ compositions were conducted in HEK-293 cells. Patch clamp recordings revealed that coexpression of Gβ ₂ γ ₂ reduced Ca _v 3.3 current density and accelerated inactivation kinetics. Interestingly, the effects were not unique to Gβ ₂ γ _2, but were mimicked by Gβ ₂ alone as well as other Gβγ dimers, with similar potencies. Deletion of the Gβ ₂ interaction site abolished the effects of Gβ ₂ γ ₂ . Importantly, these Gβ ₂ effects were reproduced in human Ca _v 3.3. Overall, our findings provide evidence that Gβ(γ) complexes inhibit Ca _v 3.3 channel activity and accelerate the inactivation kinetics through the Gβ interaction with the Ca _v 3.3 C-terminus.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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