Fig. 4. Functional and dysfunctional responses to disruptions in stoichiometry.
(A) An overabundance of STX4 in the β-cell increases the amplitude of both phases of GSIS and enhances glucose homeostasis in vivo. STX4 binds directly to F-actin and indirectly via association with the actin binding protein gelsolin. Additional units of STX4 increase the abundance of STX4-based SNARE complexes. (B) An overabundance of STX1A decreases VDCC and Kv channel activity/gating, linked to STX1A’s ability to bind to the channels and reduce function, which in vivo decreases GSIS and disrupts glucose homeostasis.