Functional Interaction of Calcium-/Calmodulin-dependent Protein Kinase II and Cytosolic Phospholipase A2

Abstract

Calcium-/calmodulin-dependent protein kinase II (CaM kinase II), a decoder of Ca2+ signals, and cytosolic phospholipase A2 (cPLA 2), an enzyme involved in arachidonate release, are involved in many physiological and pathophysiological processes. Activation of CaM kinase II in norepinephrine-stimulated vascular smooth muscle cells leads to activation of cPLA2 and arachidonic acid release. Surface plasmon resonance, mass spectrometry, and kinetic studies show that CaM kinase II binds to cPLA 2 resulting in cPLA2 phosphorylation on Ser-515 and an increase in its enzymatic activity. Phosphopeptide mapping studies with cPLA2 from norepinephrine-stimulated smooth muscle cells indicates that phosphorylation of cPLA2 on Ser-515, but not on Ser-505 or Ser-727, occurs in vivo. This novel signaling pathway for arachidonate release is shown to be cPLA2-dependent by use of a recently described and highly selective inhibitor of this enzyme.