TRANSCRIPTIONAL AND POST-TRANSLATIONAL ERK 1/2 REGULATION OF MKP-3 SPLICE VARIANTS IN BREAST CANCER CELLS

NUDLER S; MORI SEQUEIROS GARCIA MM; COHEN SABBAN JM; CASTILLO AF; PAZ C

Mar del Plata, Buenos Aires, Argentina

Congreso; LXI Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica; 2016

Sociedad Argentina de Investigación Clínica

MKP-3 is a member of the family of mitogen-activated proteinkinase phosphatase (MKPs) that specifically dephosphorylatesERK 1/2, acting as a key effector of the MAPK signal pathway.Variable expression of MKP-3 was detected in different cancertypes. In human tissues and cell lines, two splice variants ofMKP-3 are expressed: the full transcript or isoform L, and isoformS, where exon 2 is skipped. The function of MKP-3 andits isoforms in breast cancer is still not well known. The aim ofthis work was to analyze and to compare the role of P-ERK onmRNA and protein stability of both isoforms in the breast cance rcell line MDA-MB-231. Real time RT-PCR analysis showed thatboth isoforms, S and L, are induced by a mitogenic stimuli (fetalbovine serum, FBS) in a time and ERK-dependent manner.The maximal induction of L and S isoforms was detected after3 h of stimulation (1.4 and 1.8-fold, for L and S respectively).In cells stimulated with FBS for 3 h, a MEK (MAPK kinase)inhibitor (PD 98059) reduced L and S mRNA levels in a timedependent manner, reaching a 10% of the initial value after 3 hof treatment. In actinomicyn D-treated cells, the decay of bothisoforms was different. Indeed, mRNA of the L isoform showedhigher stability as compared to the S isoform (half life: 60 vs. 38min), while blockade of P-ERK signaling by PD 98059 reducedmRNA stability of both isoforms. Western blot analysis revealedthe presence of L and S proteins in MDA-MB-231 cells, being Llevels up-regulated by the MEK inhibitor. Together, our resultsshow that P-ERK regulates the expression and stability of mRNAsof both isoforms of MKP-3 but only the stability of the L protein.