Differential regulation of HMG-CoA reductase and Insig-1 by enzymes of the ubiquitin-proteasome system.

The endoplasmic reticulum (ER)-resident enzyme 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase catalyzes the rate-limiting step in sterol production and is the therapeutic target of statins. Understanding HMG-CoA reductase regulation has tremendous implications for atherosclerosis. HMG-CoA reductase levels are regulated in response to sterols both transcriptionally, through a complex regulatory loop involving the ER Insig proteins, and posttranslationally, by Insig-dependent protein degradation by the ubiquitin-proteasome system.

RGS13 regulates germinal center B lymphocytes responsiveness to CXC chemokine ligand (CXCL)12 and CXCL13.

Normal lymphoid tissue development and function depend upon directed cell migration. Providing guideposts for cell movement and positioning within lymphoid tissues, chemokines signal through cell surface receptors that couple to heterotrimeric G proteins, which are in turn subject to regulation by regulator of G protein signaling (RGS) proteins. In this study, we report that germinal center B lymphocytes and thymic epithelial cells strongly express one of the RGS family members, RGS13.

Additional 5' exons in the RGS3 locus generate multiple mRNA transcripts, one of which accounts for the origin of human PDZ-RGS3.

Regulators of G-protein signaling (RGS) proteins can be broadly divided into those that consist predominantly of an RGS domain and those that possess an RGS domain along with additional domains. RGS3 fits into both categories, as both short and longer forms exist. Recently, a novel form of mouse RGS3 that possesses a PDZ domain was identified.