Critical roles of type III phosphatidylinositol phosphate kinase in murine embryonic visceral endoderm and adult intestine

Abstract

The metabolism of membrane phosphoinositides is critical for a variety of cellular processes. 5)P 2 ] controls multiple steps of the intracellular membrane trafficking system in both yeast and mammalian cells. However, other than in neuronal tissues, little is known about the physiological functions of PtdIns(3,5)P 2 in mammals. Here, we provide genetic evidence that type III phosphatidylinositol phosphate kinase (PIPKIII), which produces PtdIns(3,5)P 2 , is essential for the functions of polarized epithelial cells. PIPKIII-null mouse embryos die by embryonic day 8.5 because of a failure of the visceral endoderm to supply the epiblast with maternal nutrients. Similarly, although intestine-specific PIPKIII-deficient mice are born, they fail to thrive and eventually die of malnutrition. At the mechanistic level, we show that PIPKIII regulates the trafficking of proteins to a cell's apical membrane domain. Importantly, mice with intestine-specific deletion of PIPKIII exhibit diarrhea and bloody stool, and their gut epithelial layers show inflammation and fibrosis, making our mutants an improved model for inflammatory bowel diseases. In summary, our data demonstrate that PIPKIII is required for the structural and functional integrity of two different types of polarized epithelial cells and suggest that PtdIns(3,5)P 2 metabolism is an unexpected and critical link between membrane trafficking in intestinal epithelial cells and the pathogenesis of inflammatory bowel disease.embryogenesis | Crohn's disease

Activity-dependent PI(3,5)P 2 synthesis controls AMPA receptor trafficking during synaptic depression

“…To determine whether PIKfyve is a regulator of synapse strength, we knocked-down PIKfyve in mouse hippocampal cultured neurons using lentiviral expression of PIKfyve-targeting shRNA and compared miniature excitatory postsynaptic currents (mEPSCs) of shRNA-expressing neurons with sham or nontargeting controls. One week postinfection, PIKfyve shRNA causes small vacuoles to appear, a phenotypic hallmark of reduced PI(3,5)P 2 levels (16,21,28,34,35). We found that the amplitude of mEPSCs in PIKfyve shRNA-transduced neurons is significantly higher than sham or nontargeting control neurons ( Fig.…”

“…The pools of PI3P that are converted to PI(3,5)P 2 may derive from the class III PI 3-kinase VPS34 (29) and/or the class II PI 3-kinase C2α (30). In vivo, depletion of PIKfyve affects both PI(3,5)P 2 and PI5P pools (10,21,24,28). Identification of PI(3,5)P 2 and PI5P protein effectors will likely reveal specific roles for each lipid.…”

“…S1). PIKfyve provides the sole source of PI(3,5)P 2 (10,15,17,(23)(24)(25)(26)(27)(28). The pools of PI3P that are converted to PI(3,5)P 2 may derive from the class III PI 3-kinase VPS34 (29) and/or the class II PI 3-kinase C2α (30).…”

Membrane dynamics in mammalian embryogenesis: Implication in signal regulation

“…During conversion to the late endosome, PtdIns3P receives a phosphate moiety via activity of phospholipid kinase PIPK(III), and becomes phosphatidylinositol 3,5-bis-phosphate (PtdIns3,5P2), which then recruits several proteins including Chmp5, which is required for forming the inwardly directed invagination of the late endosome membrane, and also essential for perigastrulation development in mice (Shim et al, 2006). Loss of PIPK(III) in mouse embryos results in formation of gigantic endosomes in cells, indicating that they are unable to transfer the limiting membranes toward inside, but rather accumulate massively, In addition, the mutant embryos are not able to complete gastrulation, indicating that the late endosome assembly is tightly coupled to embryogenesis (Takasuga et al, 2013).…”

“…Therefore, defects in late endosome maturation may cause developmental phenotypes, as seen in mutation of PIPK(III) (Takasuga et al, 2013) or the rab7 small GTP binding protein (Kawamura et al, 2012). mVam2 is a subunit of the tethering complex functioning in the late endosomes (Brocker et al, 2012).…”