Angiotensin II induces phosphorylation of glucose-regulated protein-75 in WB rat liver cells.
Studies in vascular smooth muscle cells suggest that, angiotensin II (Ang II)-mediated cellular response requires transactivation of epidermal growth factor receptor (EGF-R), and involves tyrosine phosphorylation of caveolin-1. Here we demonstrate that, exposure of WB rat liver cells to Ang II does not cause transactivation of EGF-R, but did rapidly activate p42/p44 mitogen-activated protein (MAP) kinases suggesting that it activates MAP kinases independent of EGF-R transactivation. We observed that the phospho-specific anti-caveolin-1 antibody detected a tyrosine phosphorylated, 75kDa protein in Ang II-treated cells which we identified as glucose regulated protein-75 (GRP-75). Phosphoamino acid analysis showed that Ang II induced its phosphorylation at tyrosine, serine and threonine residues and was localized to the cytoplasm. The ability of Ang-II to induce GRP-75 phosphorylation suggests that it may play a role in the protection of cytoplasmic proteins from the damaging effect of oxidative stress known to be produced during Ang-II induced signaling.
Krishna
Sharath B
SB
Department of Pharmaceutical Sciences and Cancer Biology Center, Texas Tech University Health Sciences Center, 1300 Coulter Drive, Amarillo, TX 79106, USA.
Alfonso
Lloyd F
LF
Thekkumkara
Thomas J
TJ
Abbruscato
Thomas J
TJ
Bhat
G Jayarama
GJ
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D051242:Caveolin 1 / Q000378:metabolism; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D008099:Liver / Q000166:cytology; D008565:Membrane Proteins / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010766:Phosphorylation; D051381:Rats; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D015533:Transcriptional Activation
D000596:Amino Acids; D051242:Caveolin 1; D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; D050796:STAT3 Transcription Factor; C018551:glucose-regulated proteins; D000804:Angiotensin II; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases