Expression and regulation of mitogen-activated protein kinase (MAPK) phosphatases (MKPs) in adipogenesis

Obesity has reached epidemic proportions in western industrialized countries and can be linked to a number of health risks such as hypertension, type 2 diabetes, coronary heart disease, and certain types of cancer. Obesity is due to a positive energy balance in the body that results in expansion of the adipose tissue caused by both hyperplasia and hypertrophy of adipocytes. Previous studies have found that MAPK activity is required in early stages of adipogenesis. It has also been reported that two of the MKPs, phosphatases known to dephosphorylate MAPKs, have a role in adipocyte differentiation. Based on this knowledge we carried out a systematic analysis of the expression and possible regulation of members of the MKP family during differentiation of 3T3-L1 preadipocytes. Results showed that most members of the MKP family are down-regulated during adipogenesis. We hypothesized that ectopic expression of one of the MKPs that was significantly down-regulated at early stages of differentiation, MKP-5, would have an effect on adipogenesis. Retroviral expression of MKP-5 in 3T3-L1 cells had a positive effect on adipocyte differentiation. In rodent obesity models ob/ob and Ay, most of the MKPs showed up-regulation in white adipose tissue, including MKP-5, with especially dramatic differences in subcutaneous fat depots. Although further studies are needed to verify these data, the results suggest that MKP-5, and possibly other MKPs, may have distinct roles during adipogenesis

Widespread alternative exon usage in clinically distinct subtypes of Invasive Ductal Carcinoma

Cancer cells can have different patterns of exon usage of individual genes when compared to normal tissue, suggesting that alternative splicing may play a role in shaping the tumor phenotype. The discovery and identification of gene variants has increased dramatically with the introduction of RNA-sequencing technology, which enables whole transcriptome analysis of known, as well as novel isoforms. Here we report alternative splicing and transcriptional events among subtypes of invasive ductal carcinoma in The Cancer Genome Atlas (TCGA) Breast Invasive Carcinoma (BRCA) cohort. Alternative exon usage was widespread, and although common events were shared among three subtypes, ER+ HER2−, ER− HER2−, and HER2+, many events on the exon level were subtype specific. Additional RNA-seq analysis was carried out in an independent cohort of 43 ER+ HER2− and ER− HER2− primary breast tumors, confirming many of the exon events identified in the TCGA cohort. Alternative splicing and transcriptional events detected in five genes, MYO6, EPB41L1, TPD52, IQCG, and ACOX2 were validated by qRT-PCR in a third cohort of 40 ER+ HER2− and ER− HER2− patients, showing that these events were truly subtype specific

Ubiquitination of Fibroblast Growth Factor Receptor 1 Is Required for Its Intracellular Sorting but Not for Its Endocytosis

Endocytosis and targeting of growth factor receptors for lysosomal degradation have been associated with ubiquitination of the intracellular part of the receptors. To elucidate the role of receptor ubiquitination in internalization and sorting of fibroblast growth factor receptor (FGFR), we constructed several mutants of FGFR1 in which lysines, potential ubiquitination sites, were substituted for arginines. Substitution of all lysine residues in the intracellular part of FGFR1 resulted in inactivation of the tyrosine kinase domain of the receptor. However, several multilysine FGFR1 mutants, where up to 26 of 29 lysines in the intracellular part of the receptor were mutated, retained tyrosine kinase activity. The active multilysine mutants were poorly ubiquitinated, but internalized normally, indicating that ubiquitination of the receptor is not required for endocytosis. In contrast, degradation of the multilysine mutants was dramatically reduced as the mutants were inefficiently transported to lysosomes but rather sorted to recycling endosomes. The altered sorting resulted in sustained signaling. The duration of FGFR1 signaling seems to be tightly regulated by receptor ubiquitination and subsequent sorting to the lysosomes for degradation