Biologically Active Lipids and Lipid-modulated Protein Kinase in Plants

Abstract

The career of lipids in activating protein kinase began with a brain protein kinase M which differed from camp- or cgmp-activated protein kinase from the same source (Inoue et al., 1977; Takai et al., 1977). Somewhat later it was found by Nishizuka and coworkers that this protein kinase was activated by calcium and by a heat-stable factor as coactivator which was identified as membrane lipid (Takai et al., 1979). The new protein kinase was renamed as protein kinase C (C standing for calcium). The heat stable factor was identified as the lipid activators diacylglycerol and phosphatidylserine. After protein kinase C was found, Nishizuka and coworkers soon realized that receptor-activated phospholipase C (plc) provided the lipid activator diacylglycerol in animal cells (Kishimoto et al., 1980). By now pkc not only is known to be a central enzyme in animal signal transduction but it also turned out to be a small gene family, instead of a single enzyme, the subgroups of which interact with different lipid mediators, thus making the initial picture much more complex (Asaoka et al., 1992; Nishizuka, 1992; Dekker and Parker, 1994; Exton, 1994; Liscovitch and Cantley, 1994). Pkc also provides the major paradigm in signal transduction how lipid breakdown products in the (plasma) membrane can act as lipid second messengers in between hormones, the first messengers, and their receptors and the typical target enzymes for second messengers, protein kinases and phosphatases. These latter enzymes are destined to regulate by phosphorylation/dephosphorylation the activity of other enzymes. Besides pkc, at least one additional lipid-activated protein kinase was discovered in animal cells (Pushkareva et al., 1992; Joseph et al., 1993; Kolesnik and Golde 1994) and a lipid-activated protein phosphatase (Dobrowsky et al., 1993; Hannun, 1994).KeywordsPhosphatidic AcidInositol PhospholipidPlasma Membrane ATPaSeDent Protein KinasePlant Protein KinaseThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.