Phosphorylation of RTP, an ER stress-responsive cytoplasmic protein

Biochem Biophys Res Commun. 2000 Jun 16;272(3):641-7. doi: 10.1006/bbrc.2000.2833.

Abstract

RTP, also called Drg1/Cap43/rit42/TDD5/Ndr1, was originally identified as a homocysteine-responsive gene product, and is now considered to be involved in stress responses, atherosclerosis, carcinogenesis, differentiation, androgen responses, hypoxia, and N-myc pathways. We raised an antiserum against a recombinant human RTP. Western blot analysis showed that RTP expression was induced in human umbilical vein endothelial cells under conditions causing endoplasmic reticulum stress. RTP was partially phosphorylated at seven or more sites. The phosphorylation was reversible, and was enhanced by an increased level of intracellular cAMP and inhibited by both a protein kinase A inhibitor and a calmodulin kinase inhibitor. Protein kinase A directly phosphorylated recombinant RTP in vitro. The phosphorylated forms were abundant in cells at the early log phase, and then decreased with increasing cell density. These data demonstrated that RTP is a phosphorylated stress-responsive protein, and its phosphorylation may be related to cell growth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Cell Count
  • Cell Cycle Proteins / chemistry
  • Cell Cycle Proteins / immunology
  • Cell Cycle Proteins / metabolism*
  • Cells, Cultured
  • Cyclic AMP / analogs & derivatives
  • Cyclic AMP / metabolism
  • Cyclic AMP / pharmacology
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Cycloheximide / pharmacology
  • Cytoplasm / chemistry*
  • Cytoplasm / drug effects
  • Cytoplasm / metabolism
  • Endoplasmic Reticulum / chemistry
  • Endoplasmic Reticulum / drug effects
  • Endoplasmic Reticulum / metabolism*
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / drug effects
  • Endothelium, Vascular / enzymology
  • Endothelium, Vascular / metabolism
  • Glycosylation
  • HeLa Cells
  • Homocysteine / pharmacology
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Molecular Weight
  • Phosphoprotein Phosphatases / antagonists & inhibitors
  • Phosphoprotein Phosphatases / metabolism
  • Phosphorylation / drug effects
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / immunology
  • Recombinant Proteins / metabolism
  • Transfection
  • Tunicamycin / pharmacology
  • Up-Regulation / drug effects

Substances

  • Cell Cycle Proteins
  • Intracellular Signaling Peptides and Proteins
  • N-myc downstream-regulated gene 1 protein
  • RNA, Messenger
  • Recombinant Proteins
  • Homocysteine
  • Tunicamycin
  • Cycloheximide
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Phosphoprotein Phosphatases