Phosphorylation/Dephosphorylation of c-Fos: Who does the job?

GABRIEL ORLANDO FERRERO; BEATRIZ LEONOR CAPUTTO

San MIguel de Tucumán

Congreso; Reunión de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2009

Reunión de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

In T98G cells c-Fos/endoplasmic reticulum association and consequently phospholipid synthesis activation is regulated by the phosphorylated state of c-Fos tyrosine residues. The small amount of c-Fos present in quiescent T98G cells is tyrosine-phosphorylated, is not associated to the ER and does not activate phospholipid synthesis. (Oncogene, 2007 26:3551-8). Herein, we identified which tyrosine-kinase(s) and tyrosine-phosphatase(s) are responsible for maintaining the phosphorylated or dephosphorylated state of c-Fos. An in silico search performed using the Protein Human Data Base to identify putative kinases or phosphatases acting on c-Fos evidenced c-Src and EGFR as putative kinases and TC-PTP as phosphatase, respectively. In vitro, c-Src tyrosin kinase actively phosphoryated recombinant c-Fos which was then dephosphorylated by recombinant TC-PTP. Endogenous immunoprecipitated c-Src isolated from T98G cells phosphorylated recombinant c-Fos. To evidence a possible interaction between c-Fos and different TC-PTP isoforms in vivo, point “substrate-trapping”mutated TC-PTPs were used. These substrate trappers formed stable complexes with c-Fos that co-immunoprecipitated. Taken together, these results indicate that c-Src tyrosin kinase and TC-PTP phosphatases are at least one of the kinase(s) and phsophatase(s) that regulate c-Fos tyr-phosphorylation in vivo.