FunctionThe PI(3,5)P2 regulatory complex regulates both the synthesis and turnover of phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2). In vitro, hydrolyzes all three D5-phosphorylated polyphosphoinositide substrates in the order PtdIns(4,5)P2 > PtdIns(3,5)P2 > PtdIns(3,4,5)P3. Plays a role in the biogenesis of endosome carrier vesicles (ECV) / multivesicular bodies (MVB) transport intermediates from early endosomes.
Involvement in diseaseDefects in FIG4 are the cause of Charcot-Marie-Tooth disease type 4J (CMT4J) [MIM:611228]. CMT4J is a recessive demyelinating, severe form of Charcot-Marie-Tooth disease, the most common inherited disorder of the peripheral nervous system. Charcot-Marie-Tooth disease is classified in two main groups on the basis of electrophysiologic properties and histopathology: primary peripheral demyelinating neuropathies characterized by severely reduced motor nerve conduction velocities (NCVs) (less than 38m/s) and segmental demyelination and remyelination, and primary peripheral axonal neuropathies characterized by normal or mildly reduced NCVs and chronic axonal degeneration and regeneration on nerve biopsy. Defects in FIG4 are the cause of amyotrophic lateral sclerosis type 11 (ALS11) [MIM:612577]. ALS is a neurodegenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord, resulting in fatal paralysis. Sensory abnormalities are absent. Death usually occurs within 2 to 5 years. The etiology of amyotrophic lateral sclerosis is likely to be multifactorial, involving both genetic and environmental factors. The disease is inherited in 5-10%.
Sequence similaritiesContains 1 SAC domain.
Cellular localizationEndosome membrane. Localization requires VAC14 and PIKFYVE.