Role of protein kinases C (PKC) in the relationship between the neuroendocrine and immune systems in marine mussels: The model of Mytilus galloprovincialis Lamark (1819)

摘要

Experimental evidence shows that the hemocytes of Mytilus galloprovincialis Lamark have a multivalent receptor that responds to diverse agonists provoking the activation of the immune response. The same such agonists have the property of modulating the operability of the endocrine system. The relationship between the neuroendocrine and immune systems has led to the consideration of hemocytes as a mobile immune-brain. In Mytilus galloprovincialis , two protein kinases C (PKC) mediate these processes. According to their kinetic and regulatory properties, they were classified into the families of the Ca~(2+)-independent PKCs (nPKC) and Ca~(2+)-dependent PKCs (cPKC), and named after their molecular masses, p105 and p60, respectively. Lipopolysaccharide (LPS), interleukin-2 (IL-2) and platelet-derived growth factor (PDGF) induce catecholamine synthesis but display an agonist-specific picture. The particular responses of the diverse PKC isozymes may cause the differences. These results would agree with p60 acting only on dopamine synthesizing enzyme, whereas p105 would affect norepinephrine and epinephrine production. The action of IL-2 or PDGF is related to the regulation of mussel PKC activities through the induction of mechanisms of down-regulation and balancing of p105 phosphorylation levels. As proof of the stress response, the agonists assayed induce catecholamine synthesis faster than the immune response they provoke. Also, the seasonal behavior of both processes differs in time, which proves their different timings.