Caratterizzazione e ruolo di PKC? e PKC? in modelli di differenziamento megacariocitario normale e patologico

Protein kinases C (PKC) are known to be ubiquitously distributed and to have pleiotropic effects. Isoforms epsilon (PKC?) and delta (PKC?) are involved in the regulation of cell growth, survival and differentiation; in particular, they have been also investigated for their role in the hematopoiesis and in aberrant processes of differentiation along the erythroid and megakaryocytic lineages. In this PhD thesis, the results of an in vitro study about the role of these two kinases in models of megakaryocytic (MK) differentiation, both normal and pathological, are presented. The observations about PKC? and PKC? kinetics show how these proteins have a specific modulation during the MK differentiation that results in an opposite pattern of expression and, in the murine model if compared with the human model, also a reciprocal one. In particular, in human megakaryocytopoiesis, PKC? results down-modulated, whereas in mouse its levels increase. Instead, PKC? shows a high and steady expression in maturing CD34+ MK committed, but it is strongly down-modulated during the latest phases of platelet maturation in the murine model. The study also elucidates the different pathways PKC? and PKC? work through, being an inhibitory action of PKC? on RhoA during proplatelets (ppt) formation in the mouse model while, in the human MK differentiation, platelets production is regulated by PKC? through Bcl-xL. In this dissertation it is also demonstrated how in an aberrant megakaryocytopoiesis, as in the pathologic model of primary myeloproliferative neoplasm (PMF), PKC? is strongly deregulated and it results in an altered Bcl-xL expression. A forced down-modulation of this kinase restores a normal MK differentiation and ppt maturation. Therefore, the data presented show that PKC? and PKC? play a key role in proper megakaryocyte maturation and that PKC? could be a potential new therapeutic target for PMF.