Partner of stromal interaction molecule 1 (POST) (POST)

Partner of stromal interaction molecule 1 (POST), also known as SLC35G1 or TMEM20, is a 10-transmembrane-spanning protein that plays a critical role in regulating intracellular calcium homeostasis. It functions as a scaffolding molecule that, upon depletion of endoplasmic reticulum (ER) calcium stores, facilitates the binding of the ER calcium sensor STIM1 to a variety of plasma membrane and organellar transporters, including the plasma membrane Ca2+ ATPase (PMCA), the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA), and the Na+/K+-ATPase. By recruiting STIM1 to these targets, the POST complex modulates their activity—for instance, by inhibiting PMCA-mediated calcium extrusion to sustain elevated cytosolic calcium levels necessary for signaling. Beyond ion transporters, POST also associates with nuclear transport proteins like importins and exportins, suggesting a broader role in coordinating cellular responses to calcium store depletion. Given its central role in the store-operated calcium entry (SOCE) pathway, POST is a potential therapeutic target for diseases characterized by calcium dysregulation, such as certain immune disorders and cancers.

Other names

SLC35G1TMEM20Solute carrier family 35 member G1Transmembrane protein 20Partner of STIM1

POST acts as a scaffolding protein that facilitates the interaction between STIM1 and various transporters, including PMCA, SERCA, Na+/K+-ATPase, and nuclear importins/exportins, upon endoplasmic reticulum calcium depletion to modulate calcium signaling and transport activity.