Luminal Chloride-dependent Activation of Endosome Calcium Channels

Abstract

Although Ca 2+ release from early endosomes (EE) is important for the fusion of primary endosomes, the presence of an ion channel responsible for releasing calcium from the EE has not been shown. A recent proteomics study has identified the TRPV2 channel protein in EEs, suggesting that TRP-like Ca 2+ channels may be in endosomes. The submicron size of endosomes has made it difficult to study their ion channels in the past. We have overcome this problem by generating enlarged EEs with help of a hydrolysis deficient SKD1/VPS4B mutant in HEK293 cells. Here we report the first patch-clamp recording of a novel Endosome Calcium Channel (ECC) in these enlarged EEs.