MicroRNA-203 regulates caveolin-1 in breast tissue during caloric restriction.

Caloric restriction has been shown to increase lifespan in several organisms and to delay onset of age-related diseases. The transcriptional response to caloric restriction has been studied for mRNAs, while the microRNA signature following caloric restriction remains unexplored. Here, we characterize the microRNA expression in mouse breast tissue before and after caloric restriction, reporting several changes in the microRNA expression profile. In particular, miR-203 is found to be highly induced by caloric restriction, and we demonstrate that caveolin-1 as well as p63 are direct targets of miR-203 in vivo during caloric restriction. Using tissue culture models, we suggest that this regulation is important in both mouse and human. In conclusion, we show that the microRNA response induced by caloric restriction can regulate important factors in processes such as longevity and aging and is an integral and important component of the cellular response to caloric restriction.

Parkin interacts with LIM Kinase 1 and reduces its cofilin-phosphorylation activity via ubiquitination.

Mutations in the PARKIN (PARK2) gene have been found in the majority of early-onset familial Parkinson's disease (PD) patients with autosomal recessive juvenile parkinsonism (ARJP). Parkin protein functions as an ubiquitin (E3) ligase that targets specific proteins for degradation in the 26S proteasome. Here, based on a mass spectrometry analysis of the human dopaminergic neuroblastoma-derived cell line SH-SY5Y that over-expresses parkin, we found that parkin may suppress cofilin phosphorylation. LIM Kinase 1 (LIMK1) is the upstream protein that phosphorylates cofilin, an actin depolymerizing protein. Thus, we postulated a possible connection between parkin and LIMK1. Our studies in other cell lines, using co-transfection assays, demonstrated that LIMK1 and parkin bind each other. LIMK1 also interacted with previously known parkin interactors Hsp70 and CHIP. Parkin enhanced LIMK1-ubiquitination in the human neuroblastoma-derived BE(2)-M17 cell line, but not in the human embryonic kidney-derived HEK293 cell line. In fact, parkin-over-expression reduced the level of LIMK1-induced phosphocofilin in the BE(2)-M17 cells but not in the HEK293 cells. Additionally, in simian kidney-derived COS-7 cells, parkin-over-expression reduced LIMK1-induced actin filament accumulation. LIMK1 in cultured cells regulates parkin reversibly: LIMK1 did not phosphorylate parkin but LIMK1 overexpression reduced parkin self-ubiquitination in vitro and in HEK293 cells. Furthermore, in the cells co-transfected with parkin and p38, LIMK1 significantly decreased p38-ubiquitination by parkin. These findings demonstrate a cell-type dependent functional interaction between parkin and LIMK1 and provide new evidence that links parkin and LIMK1 in the pathogenesis of familial PD.