title: Upregulation of G protein-linked receptor kinases with advancing age in rat aorta.
abstract: The age-related decline in beta-adrenergic receptor (beta-AR)-mediated vasorelaxation is associated with desensitization of beta-ARs without significant downregulation. The primary mode of this homologous beta-AR desensitization, in general, is via G protein receptor kinases (GRK). Therefore, we hypothesize that age-related changes in GRKs are causative to this etiology in rat aorta. Herein, we investigate the activity and cellular distribution (cytoplasmic vs. membrane) of several GRK isoforms and beta-arrestin proteins. GRK activity was assessed in extracts from aortic tissue of 6-wk, 6-mo, 12-mo, and 24-mo-old male Fischer-344 rats using a rhodopsin phosphorylation assay. We also performed immunoblots on lysates from aorta with specific antibodies to GRK-2, -3, -5, and beta-arrestin-1. Results show an age-related increase in GRK activity. Furthermore, expression of GRK-2 (cytoplasmic and membrane), GRK-3 (cytoplasmic and membrane), and beta-arrestin (soluble) increased with advancing age, whereas GRK-5 (membrane) expression remained unchanged. These results suggest that age is associated with increased activity and expression of specific GRKs. This increase likely results in enhanced phosphorylation and desensitization of beta-ARs. These biochemical changes are consistent with observed aging physiology.
authors.affiliation: Portland Veterans Affairs Medical Center, Research Service, Portland, Oregon 97201, USA.
authors.forename: W E
authors.initials: WE
authors.lastname: Schutzer
authors.forename: J F
authors.initials: JF
authors.lastname: Reed
authors.forename: M
authors.initials: M
authors.lastname: Bliziotes
authors.forename: S L
authors.initials: SL
authors.lastname: Mader
mesh_terms: D000375:Aging; D000818:Animals; D001011:Aorta / Q000201:enzymology* / Q000648:ultrastructure; D019390:Arrestins / Q000032:analysis / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis / Q000378:metabolism*; D003593:Cytoplasm / Q000201:enzymology; D054770:G-Protein-Coupled Receptor Kinase 3; D054774:G-Protein-Coupled Receptor Kinase 5; D015151:Immunoblotting; D007527:Isoenzymes / Q000032:analysis / Q000378:metabolism; D008297:Male; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D012243:Rhodopsin / Q000378:metabolism; D014664:Vasodilation; D051552:beta-Adrenergic Receptor Kinases; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins
chemical_list: C000605256:Arrb1 protein, rat; D019390:Arrestins; D007527:Isoenzymes; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D012243:Rhodopsin; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D054770:G-Protein-Coupled Receptor Kinase 3; C517851:Grk3 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054774:G-Protein-Coupled Receptor Kinase 5; C517897:Grk5 protein, rat