• Register
Forgot Password

If you have forgotten your password you can enter your email here and get a temporary password sent to your email.


Leaving Community

Are you sure you want to leave this community? Leaving the community will revoke any permissions you have been granted in this community.


Intramembrane glycine mediates multimerization of Insig-2, a requirement for sterol regulation in Chinese hamster ovary cells.

Sterol-induced binding of endoplasmic reticulum (ER) membrane proteins Insig-1 and Insig-2 to SREBP cleavage-activating protein (Scap) and HMG-CoA reductase triggers regulatory events that limit cholesterol synthesis in animal cells. Binding of Insigs to Scap prevents proteolytic activation of sterol-regulatory element binding proteins (SREBPs), membrane-bound transcription factors that enhance cholesterol synthesis, by trapping Scap-SREBP complexes in the ER. Insig binding to reductase causes ubiquitination and subsequent proteasome-mediated degradation of the enzyme from ER membranes, slowing a rate-limiting step in cholesterol synthesis. Here, we report the characterization of mutant Chinese hamster ovary cells, designated SRD-20, that are resistant to 25-hydroxycholesterol, which potently inhibits SREBP activation and stimulates degradation of reductase. SRD-20 cells were produced by mutagenesis of Insig-1-deficient SRD-14 cells, followed by selection in 25-hydroxycholesterol. DNA sequencing reveals that SRD-20 cells harbor a point mutation in one Insig-2 allele that results in production of a truncated, nonfunctional protein, whereas the other allele contains a point mutation that results in substitution of glutamic acid for glycine-39. This glycine residue localizes to the first membrane-spanning segment of Insig-2 and is also present in the corresponding region of Insig-1. Mutant forms of Insig-1 and Insig-2 containing the Glu-to-Gly substitution fail to confer sterol regulation upon overexpressed Scap and reductase. These studies identify the intramembrane glycine as a key residue for normal sterol regulation in animal cells.

Pubmed ID: 19617589


  • Lee PC
  • DeBose-Boyd RA


Journal of lipid research

Publication Data

January 16, 2010

Associated Grants

  • Agency: NHLBI NIH HHS, Id: HL-20948
  • Agency: Howard Hughes Medical Institute, Id:

Mesh Terms

  • Amino Acid Sequence
  • Animals
  • CHO Cells
  • Cricetinae
  • Cricetulus
  • Endoplasmic Reticulum
  • Glycine
  • Hydroxycholesterols
  • Hydroxymethylglutaryl CoA Reductases
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Molecular Sequence Data
  • Mutation
  • Protein Multimerization
  • Sequence Alignment