CALCIUM ION DEPENDENT PHOSPHOKINASE C ISOFORMS IN ADAPTATION/INFLAMATION

University Of Colorado Denver, Aurora CO

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Abstract

PKC isoforms differ in structure, CA++ dependency (cPKC) and regulation by lipids, but are present in all tissues examined. The specific combination of isoforms expressed are characteristic of that cell phenotype. This suggests that these isoforms do not have overlapping functions. Although functional cardioprotection induced by preconditioning is inhibited by PKC inhibitors, it is not clear what roles the isoforms play. Several PKC- linked stimuli, including Ca++ preconditioning, mediate different patterns of isoform translocation to different myocellular compartments. Several lines of evidence suggest that each receptor stimulated, isoform-profile encodes distinct mechanisms of protection. Comparison of different post- injury outcomes indicates that stimuli conferring preconditioning against post-ischemic mechanical dysfunction do not automatically protect against cell-death. Further, different degrees of functional protection against progressively severe ischemia indicates that preconditioning stimuli differ in their potency. Significantly, outcomes such as functional protection do not appear to be simply correlated with either the number of isoform engaged or the extent of translocation, indicating the importance of spatially precise isoform translocation, for the correct duration. This leads to the hypothesis that 'PKC' mediated mechanisms of protection or inflammation may be encoded by distinct combinations of PKC isoforms in specific compartments. In this proposal we will build on previous work on cardiac functional protection to 1. evaluate the efficacy of a set of preconditioning stimuli against cardiac apoptosis and infarction that occurs after severe ischemia. Map the spatial and temporal translocation for each isoform engaged by this set of cardiac stress, receptor, and direct PKC-linked stimuli. 3. Determine the specific role of the cPKC isoforms in mediating mechanisms of cardioprotection against post-ischemic dysfunction, infarction and apoptosis. Several heart cells including resident leukocytes express cPKC isoforms. Neutrophils and macrophages are important in systemic post-traumatic inflammation and when stimulated by appropriate receptor, are known to involves PKC in their cytotoxic functions. We will therefore investigate whether PKC linked receptors also translocate unique isoform profiles in these inflammatory leukocytes, by 4. determining the spatial and temporal translocation of isoforms after prototypic inflammatory stimuli and 5. assessing the role of the cPKC isoforms in mediating the cytotoxicity of appropriately stimulated isolated human neutrophils and rat macrophages.