Protein C activity in the central nervous system of Hirudo medicinalis

A wide variety of neurootrasmitters and hormones mediate many of their actions through the activation of the Ca ++ /phospholipid/ diacylglycerol dependent protein kinase C (PKC). In nerve cells. PKC1 has been shown to be involved in the regulation of ion channels and neurotrasmitter release. Recently, since PKC has been proposed to play a crucial role in synaptic plasticity we have started the study of PKC activity and its cellular substrates in the central nervous system of the leech Hirudo medicinalis, which is considered a good model for learning processes. We have measured PKC activity in homoqenates, cytosolic and particulate fractions of leech central nervous system, using histone as phosphate aceptor, 32P-ATP, Ca++, phosphatidyl serine and oleylacetylglycerol at different concentrations. The phosphorylation mix was spotted ont phosphocellulose filter paper and radioactivity measured C activity was higher in cytosolic than in particulte fractions. Phosphatidyl serine diacylglycerol enhanced the ezymatic activity in a dose dependent manner, even in the absence of calcium in the phosphorylation mix. Endogenous substrates of PKC have been studied using electrophoresis and autoradiography. Most of the substrates of the calcium/calmodulin dependent protein kinase are substrates of the PKC The identification of PKC substrates is a first step in the invetigation of the role of PKC in learning process, in Hirudo medicinalis.