Albumin overload up-regulates MKP-1 in renal tubular cells

GOROSTIZAGA AB; GOMEZ NV; MORI SEQUEIROS GARCÍA MM; RECA S; MENDEZ CF; PAZ C

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2012

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

In renal tubular cells, albumin overload promotes both the transientactivation of MAP kinases (ERK1/2, JNK1/2 and p38) andreticulum stress (RS). MAP kinase phosphatases (MKPs) are induced by several stimuli to inactivate MAPKs. MKP-1 is a nuclear MKP that dephosphorylates all MAPKs. Here we analyzed the effect of albumin (BSA, 20 mg/ml) in a proximal tubule-derived cell line of opossum (Didelphis virginiana) origin (OK cells). Western blot analysis showed that BSA promoted MKP-1 accumulation after 1 h of stimulation (2-fold). Since the MKP-1genome sequence of opossum is not completely characterized, wedesigned oligonucleotides based on the sequence described for the highly related , to isolate the MKP-1 cDNA from OK cells by RT-PCR. Sequence homology between species of the isolated cDNA was 98%. Next, using specific oligonucleotides, we evaluated the effect of BSA on MKP-1 mRNA levels. BSA transiently increased mRNA levels (2-fold after 1h), an effect blocked by actinomycin D, which suggests that BSA activates MKP-1 gene transcription. BSA also increased mRNA levels of GRP78 protein, an RS marker, and an inhibitor of ERK1/2 activation (PD98059, 50 μM), prevented this effect. Collectively, our data indicate that MKP-1 is induced by BSA at a transcriptional level and suggest that it may contribute to turn off ERK-dependentevents triggered by BSA