Phosphatidylinositol 3-phosphate 5-kinase (PIKfyve) is an AMPK target participating in contraction-stimulated glucose uptake in skeletal muscle

Phosphatidylinositol 3-phosphate 5-kinase (PIKfyve), the lipid kinase that phosphorylates PtdIns3P to PtdIns(3,5)P2, has been implicated in insulin-stimulated glucose uptake. We investigated whether PIKfyve could also be involved in contraction/AMP-activated protein kinase (AMPK)-stimulated glucose uptake in skeletal muscle. Incubation of rat epitrochlearis muscles with YM201636, a selective PIKfyve inhibitor, reduced contraction- and AICA riboside (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside)-stimulated glucose uptake. Consistently, PIKfyve knockdown in C2C12 myotubes reduced AICA riboside-stimulated glucose transport. Furthermore, muscle contraction increased PtdIns(3,5)P2 levels and PIKfyve phosphorylation. AMPK phosphorylated PIKfyve at Ser307 both in vitro and in intact cells. Following subcellular fractionation, PIKfyve recovery in a crude intracellular membrane fraction was increased in contracting versus resting muscles. Also in opossum kidney cells, wild-type, but not S307A mutant, PIKfyve was recruited to endosomal vesicles in response to AMPK activation. We propose that PIKfyve activity is required for the stimulation of skeletal muscle glucose uptake in response to contraction/AMPK activation. PIKfyve is a new AMPK substrate whose phosphorylation at Ser307 could promote PIKfyve translocation to endosomes for PtdIns(3,5)P2 synthesis to facilitate GLUT4 translocation.