PHOSPHOLIPASE A(2) AND PROTEIN-KINASE-C ENZYMATIC-ACTIVITIES AND THEIR INTERACTIONS IN HYDRA-VULGARIS

Recent reports have assigned to activation of phospholipase A(2) (PLA( 2)), with subsequent production of arachidonic acid (AA) and its deriv atives, and to stimulation of protein kinase C (PKC), a key role in th e control of body pattern, tentacle regeneration, and bud formation in two Hydra species, Experiments conducted in vivo suggested also the o ccurrence of a bidirectional interaction between the two enzymes durin g these processes. Here we describe for the first time the simultaneou s partial characterization of PLA(2) and PKC activities in a hydrozoan species, the freshwater Hydra vulgaris. PLA(2) activity was found to be associated with membrane fractions, dependent on pH and on millimol ar Ca2+ concentrations and counteracted by a specific inhibitor of mam malian membrane PLA(2), oleyloxyethyl-phosphoryl-choline (OOPC). A PKC -like enzyme with a molecular weight of about 70 kDa was partially pur ified from cytosolic extracts. Its activity was also found to depend o n Ca2+ as well as phosphatidylserine, but was not influenced by AA. Co nversely, the PKC activator tetradecanoylphorbol-11-acetate (TPA) indu ced PLA(2) activation and AA liberation in H. vulgaris polyps in vivo, While PKC-PLA(2) interactions have been extensively investigated in m ammals, the present study represents the first example of PKC-induced activation of an invertebrate PLA(2).