Protein tyrosine phosphorylation activates rat splenic type II phosphatidylinositol 4-kinase in vitro

Plant phosphoinositide signaling - dynamics on demand

Eukaryotic membranes contain small amounts of lipids with regulatory roles. An important class of such regulatory lipids are phosphoinositides (PIs). Within membranes, PIs serve as recruitment signals, as regulators of membrane protein function or as precursors for second messenger production, thereby influencing a multitude of cellular processes with key importance for plant function and development. Plant PIs occur locally and transiently within membrane microdomains, and their abundance is strictly controlled. To understand the functions of the plant PI-network it is important to understand not only downstream PI-effects, but also to identify and characterize factors contributing to dynamic PI formation. This article is part of a Special Issue entitled: Plant Lipid Biology edited by Kent D. Chapman and Ivo Feussner.

Type II phosphatidylinositol 4-kinase β associates with TCR-CD3 ζ chain in Jurkat cells

Phosphatidylinositol lipid signaling cascades are integral part of TCR-CD3 signaling. The mechanisms by which phosphatidylinositol kinases are coupled to TCR-CD3 complex remain elusive. Here we report an association of type II PtdIns 4-kinase with TCR-CD3 zeta chain upon cross-linking. Mapping studies have revealed that the C-terminal ITAM is critical for docking of the enzyme on the zeta chain. The association is shown to be tyrosyl phosphorylation dependent as mutation of Y-151 and Y-142 on the C-terminal ITAM disrupts interaction of the two proteins. Identification of the associated type II PtdIns 4-kinase revealed that the beta isoform of the enzyme interacts with the zeta chain in vivo.

Resveratrol inhibits type II phosphatidylinositol 4-kinase: A key component in pathways of phosphoinositide turn over

Resveratrol has anti-inflammatory, cardio protective and cancer chemopreventive properties. The molecular targets for resveratrol in early signaling cascades are not well understood. Resveratrol inhibits type II PtdIns 4-kinase but not PtdIns 3-kinase activity in vitro. Resveratrol directly binds to the enzyme with a Kd of 7.2 microM. Kinetic studies show that resveratrol competes with PtdIns binding. Inhibition of PtdIns 4-kinase activity by resveratrol/phenylarsine oxide reduces Jurkat cell adhesion to matrigel/fibronectin coated surfaces, suggesting a role for type II PtdIns 4-kinase in lymphocyte infiltration to the sites of inflammation.