Transformer 2β homolog (Drosophila) (TRA2B) Regulates Protein Kinase C δI (PKCδI) Splice Variant Expression during 3T3L1 Preadipocyte Cell Cycle

Background: PKC modulates cellular differentiation and proliferation. Results: Splice factor TRA2B regulates alternative splicing of PKCI. Conclusion: PKCI is a gate-keeper of adipocyte differentiation. Significance: Understanding the role and regulation of PKCI during adipogenesis may contribute toward developing a novel target for managing obesity and its co-morbidities. Obesity is characterized by adipocyte hyperplasia and hypertrophy. We previously showed that PKC expression is dysregulated in obesity (Carter, G., Apostolatos, A., Patel, R., Mathur, A., Cooper, D., Murr, M., and Patel, N. A. (2013) ISRN Obes. 2013, 161345). Using 3T3L1 preadipocytes, we studied adipogenesis in vitro and showed that expression of PKC splice variants, PKCI and PKCII, have different expression patterns during adipogenesis (Patel, R., Apostolatos, A., Carter, G., Ajmo, J., Gali, M., Cooper, D. R., You, M., Bisht, K. S., and Patel, N. A. (2013) J. Biol. Chem. 288, 26834-26846). Here, we evaluated the role of PKCI splice variant during adipogenesis. Our results indicate that PKCI expression level is high in preadipocytes and decreasing PKCI accelerated terminal differentiation. Our results indicate that PKCI is required for mitotic clonal expansion of preadipocytes. We next evaluated the splice factor regulating the expression of PKCI during 3T3L1 adipogenesis. Our results show TRA2B increased PKCI expression. To investigate the molecular mechanism, we cloned a heterologous splicing PKC minigene and showed that inclusion of PKC exon 9 is increased by TRA2B. Using mutagenesis and a RNA-immunoprecipitation assay, we evaluated the binding of Tra2 on PKCI exon 9 and show that its association is required for PKCI splicing. These results provide a better understanding of the role of PKCI in adipogenesis. Determination of this molecular mechanism of alternative splicing presents a novel therapeutic target in the management of obesity and its co-morbidities.