High impact information on FIG4

• Synthesis is catalyzed by the PI3P 5-kinase Fab1p, and turnover is catalyzed by the PI3,5P2 5-phosphatase Fig4p [1].
• Three of the proteins encoded by these genes, Fig1p, Fig2p, and Fig4p, are dispensible for cell polarization in uniform concentrations of mating pheromone, but are required for normal cell polarization in mating mixtures, conditions that involve cell-cell communication [2].
• Fig4p is a member of a family of eukaryotic proteins that contain a domain homologous to the yeast Sac1p [2].
• Consistent with these observations, we found that Fig4 physically associates with Vac14 in a common membrane-associated complex [3].
• More recently, a suppressor of vac7Delta mutants was identified and shown to encode a putative phosphoinositide phosphatase, Fig4 [3].

Biological context of FIG4

• We also identified a mutant allele of FIG4, whose gene product contains a Sac1 polyphosphoinositide phosphatase domain, which suppresses vac7Delta mutant phenotypes [4].
• In Saccharomyces cerevisiae, the SAC1 gene encodes a polyphosphoinositide phosphatase (PPIPase) that modulates the levels of phosphoinositides, which are key regulators of a number of signal transduction processes [5].

Anatomical context of FIG4

• Analysis of a Fig4-GFP fusion protein revealed that the Fig4 phosphatase is localized to the limiting membrane of the vacuole [3].

Other interactions of FIG4

• Our studies indicate that Vac14 both positively regulates Fab1 kinase activity and directs the localization/activation of the Fig4 PtdIns(3,5)P2 phosphatase [3].

References