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 derivatives, and to stimulation of protein kinase C (PKC), a key role in the control of body pattern, tentacle regeneration, and bud formation in two Hydra species, Experiments conducted in vivo suggested also the occurrence of a bidirectional interaction between the two enzymes during these processes. Here we describe for the first time the simultaneous 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 millimolar Ca2+ concentrations and counteracted by a specific inhibitor of mammalian membrane PLA(2), oleyloxyethyl-phosphoryl-choline (OOPC). A PKC-like enzyme with a molecular weight of about 70 kDa was partially purified from cytosolic extracts. Its activity was also found to depend on Ca2+ as well as phosphatidylserine, but was not influenced by AA. Conversely, the PKC activator tetradecanoylphorbol-11-acetate (TPA) induced PLA(2) activation and AA liberation in H. vulgaris polyps in vivo, While PKC-PLA(2) interactions have been extensively investigated in mammals, the present study represents the first example of PKC-induced activation of an invertebrate PLA(2).