FIG4 and Fabry disease: In addition, during activation of the lysosomal Ca2+-activated potassium channel (BK), TRPML1-dependently rescues aberrant lysosomal storage in NPA and Fabry disease [9], and loss of FIG4 (polyphosphoinositide phosphatase) and PYKfyve (FYVE finger-containing phosphoinositide kinase), which are both involved in the synthesis of the endogenous TRPML/TPC agonist PI(3,5)P2, is associated with neurological or neurodegenerative disease phenotypes [9,10,11] that can be rescued by TRPML1 activation [11].