Distinct transcriptional control and action of fibroblast growth factor receptor 4 in differentiating skeletal muscle cells.

Although FGF signaling promotes myoblast proliferation and represses myogenic differentiation, one of the FGF receptors (FGFR), FGFR4, is expressed mainly in mature skeletal muscle. Disruption of FGFR4 signaling interrupts chick limb muscle formation. To determine the developmental regulation of FGFR4 expression, we compared the transcriptional control and action of FGFR4 in myoblasts and myotubes.

Overexpression of the endoplasmic reticulum 60 protein ER-60 downregulates apoB100 secretion by inducing its intracellular degradation via a nonproteasomal pathway: evidence for an ER-60-mediated and pCMB-sensitive intracellular degradative pathway.

Co- and posttranslational regulation of apolipoprotein B (apoB) has been postulated to involve degradation by both proteasomal and nonproteasomal pathways; however, nonproteasomal mechanisms of apoB degradation are currently unknown. We have previously demonstrated an intracellular association of newly synthesized apoB with endoplasmic reticulum (ER)-60, an ER-localized protein, possessing both proteolytic and chaperone activities. In the present paper, adenoviral expression vectors containing rat ER-60 cDNA were used to achieve dose- and time-dependent overexpression of ER-60 to investigate its role in apoB100 turnover.

Expression of human hepatic lipase in the rabbit model preferentially enhances the clearance of triglyceride-enriched versus native high-density lipoprotein apolipoprotein A-I.

Background: We have shown previously that triglyceride (TG) enrichment of HDL, as occurs in hypertriglyceridemic states, contributes to HDL lowering in humans by enhancing the clearance of HDL apolipoprotein (apo) A-I from the circulation. In the New Zealand White rabbit, an animal naturally deficient in hepatic lipase (HL), we demonstrated that TG enrichment of HDL per se is not sufficient to enhance HDL clearance in the absence of ex vivo lipolysis by HL. Here, we examined in the rabbit the interaction between in vivo HL lipolytic action and HDL TG enrichment on the subsequent metabolic clearance of HDL apoA-I.

Pax-6 activates endogenous proglucagon gene expression in the rodent gastrointestinal epithelium.

The proglucagon gene encodes pancreatic glucagon and the glucagon-like peptides, which exert diverse effects on nutrient absorption and assimilation. The therapeutic potential of glucagon-like peptide-1 (GLP-1) has fostered interest in development of cellular engineering approaches to augment endogenous intestinal-derived GLP-1 for the treatment of type 2 diabetes. We have used adenovirus technology to examine the potential roles of the transcription factors Cdx-2/3 and Pax-6 as activators of endogenous proglucagon gene expression in enteroendocrine cell lines and in nontransformed rat intestinal cells.