Activation of protein kinase C family members by the novel polyphosphoinositides PtdIns-3,4-P2 and PtdIns-3,4,5-P3.

摘要: The effect of phosphoinositides on the activity protein kinase C (PKC) isotypes was investigated. PKC alpha, beta I, II, gamma, delta, epsilon, eta, and zeta were expressed in baculovirus-infected insect cells purified by column chromatography. calcium-activated gamma not significantly activated any investigated (phosphatidylinositol-4-phosphate (PtdIns-4-P), PtdIns-3-P, PtdIns-4,5-P2, PtdIns-3,4-P2, PtdIns-3,4,5-P3) when added presence concentrations phosphatidylserine that give maximal stimulation. calcium-insensitive theta also showed little response to PtdIns-4-P, or PtdIns-4,5-P2 these lipids phosphatidylserine. In contrast, PtdIns-3,4-P2 PtdIns-3,4,5-P3 caused a 5-15-fold stimulation enzymes compared with alone. 50% epsilon occurred this lipid present at about 1% carrier (about 100 nM). These had baculovirus-expressed zeta, which constitutively active. A short chain version PtdIns-3,4,5-P3, dioctanoyl-PtdIns-3,4,5-P3, eta absence other lipids, whereas dihexanoyl-PtdIns-4,5-P2, did not. Since are nominally absent unstimulated appear within seconds minutes various cell activators, could act as second messengers activate vivo.