Phosphatidic acid regulates the affinity of the murine phosphatidylinositol 4-phosphate 5-kinase-10 for phosphatidylinositol-4-phosphate

作者：Jarquin Pardo Marta; Fitzpatrick Abbie; Galiano Floyd J; First Eric A; Davis J Nathan^*

来源：Journal of Cellular Biochemistry, 2007, 100(1): 112-128.

DOI：10.1002/jcb.21027

• phosphatidic acid
• type I phosphatidylinositol 4-phosphate 5-kinase
• PIP Kinase
• phosphatidylinositol 4,5 bisphosphate

Type I phosphatidylinositol 4-phosphate 5-kinase (PI4P5K) catalyzes the phosphorylation of phosphatidylinositol 4 phosphate [PI(4)P] at carbon 5, producing phosphatidylinositol 4,5 bisphosphate [PI(4,5)P2]. Phosphatidic acid (PA) activates PI4P5K in vitro and plays a central role in the activation of PIP5K pathways in vivo. This report demonstrates that actin fiber formation in murine fibroblasts involves PA activation of PIP5Ks and defines biochemical interactions between PA and the PIP5Ks. Inhibition of phospholipase D production of PA results in the loss of actin fibers. Overexpression of the beta isoform of the type I murine phosphatidylinositol 4-phosphate 5-kinase (mPIP5K-1 beta) maintains actin fiber structure in the face of phospholipase D inhibition. PA activates mPIP5K-1 beta by direct binding to mPIP5K-1 beta through both electrostatic and hydrophobic interactions, with the fatty acid acyl chain length and degree of saturation acting as critical determinants of binding and activation. Furthermore, kinetic analysis suggests that phosphorylation of the PI(4)P substrate does not follow classical Michaelis-Menten kinetics. Instead, the kinetic data are consistent with a model in which mPIP5K-1 beta initially binds to the lipid micelle and subsequently binds the PIMP substrate. In addition, the kinetics indicate substrate inhibition, suggesting that mPIP5K-1 beta contains an inhibitory PI(4)P-binding site. These results suggest a model in which mPIP5K-1 beta is surrounded by PI(4)P, but is unable to catalyze its conversion to PI(4,5)P2 unless PA is bound.

• 出版日期2007-1-1