Skip to main content
. Author manuscript; available in PMC: 2012 Sep 1.
Published in final edited form as: Cell Calcium. 2011 May 31;50(3):288–294. doi: 10.1016/j.ceca.2011.04.009

Figure 2. Models of the role of the activation of TRPML1 by PI(3,5)P2 in the endocytic pathway.

Figure 2

A) TRPML1 as an organellar proximity sensor: TRPML1 activation by PI(3,5)P2 in the opposing membrane promotes organellar fusion. The lack of Ca2+ release through TRPML1 in the absence of PI(3,5)P2 binding precludes conformational change in SNARE that promotes fusion (step 1). The proximity of TRPML1-containing and target membranes promotes TRPML1 interaction with PI(3,5)P2 (step 2), Ca2+ release through TRPML1 (step 3) and membrane fusion (step 4). B) TRPML1 activation by delivery to PI(3,5)P2-rich compartments. TRPML1 is inactive in the delivery vesicles, but its activation is promoted by its delivery to PI (3,5)P2-rich organelles (steps 5 and 6). This is followed by Ca2+ release through TRPML1 (step 7) and membrane fusion (step 8).