Activation and targeting of extracellular signal-regulated kinases by β-arrestin scaffolds

Using both confocal immunofluorescence microscopy and biochemical approaches, we have examined the role of β-arrestins in the activation and targeting of extracellular signal-regulated kinase 2 (ERK2) following stimulation of angiotensin II type 1a receptors (AT1aR). In HEK-293 cells expressing hemagglutinin-tagged AT1aR, angiotensin stimulation triggered β-arrestin-2 binding to the receptor and internalization of AT1aR-β-arrestin complexes. Using red fluorescent protein-tagged ERK2 to track the subcellular distribution of ERK2, we found that angiotensin treatment caused the redistribution of activated ERK2 into endosomal vesicles that also contained AT1aR-β-arrestin complexes. This targeting of ERK2 reflects the formation of multiprotein complexes containing AT1aR, β-arrestin-2, and the component kinases of the ERK cascade, cRaf-1, MEK1, and ERK2. Myc-tagged cRaf-1, MEK1, and green fluorescent protein-tagged ERK2 coprecipitated with Flag-tagged β-arrestin-2 from transfected COS-7 cells. Coprecipitation of cRaf-1 with β-arrestin-2 was independent of MEK1 and ERK2, whereas the coprecipitation of MEK1 and ERK2 with β-arrestin-2 was significantly enhanced in the presence of overexpressed cRaf-1, suggesting that binding of cRaf-1 to β-arrestin facilitates the assembly of a cRaf-1, MEK1, ERK2 complex. The phosphorylation of ERK2 in β-arrestin complexes was markedly enhanced by coexpression of cRaf-1, and this effect is blocked by expression of a catalytically inactive dominant inhibitory mutant of MEK1. Stimulation with angiotensin increased the binding of both cRaf-1 and ERK2 to β-arrestin-2, and the association of β-arrestin-2, cRaf-1, and ERK2 with AT1aR. These data suggest that β-arrestins function both as scaffolds to enhance cRaf-1 and MEK-dependent activation of ERK2, and as targeting proteins that direct activated ERK to specific subcellular locations.

The Satirist, or Monthly meteor ...

Editors: Oct. 1807-June 1812, George Manners.--July 1812-Aug. 1814, William Jerdan.

Men and books. Collected and reprinted from the Canadian Medical Association Journal.

"Edition limited to 200 copies."

Abstract of the returns of the overseers of the poor in Massachusetts, for the year ending November 1, 1848 /

Cover title: Pauper abstract for 1848.

Konzert für die Orgel, mit zwei Manualen und Pedal, nach Vivaldi.

"Edition Peters, No. 3002."

A treatise on criminal pleading, with precedents of indictments, special pleas, &c. Adapted to practice.

Mode of access: Internet.

Commentaries on the law of suretyship, and the rights and obligations of the parties thereto, and herein of obligations in solido, under the laws of England, Scotland, and other states of Europe, the British colonies, and United States of America, and on the conflict of those laws.

"List of continental authors cited": p. [xi]-xvi; "American authorities": p. [xvii]-xviii.

Six easy duets for two violins, op. 61

Mode of access: Internet.

The face of the earth =Das antlitz der erde /

Vol. 5: Indexes and maps.

The M. P. for Russia;

Appendix A: The traditional policy of Russia (from "Russia and England", 1880) vol. II, p. 457-470; Appendix B: A nation's protest against war (from the "Northern echo" of January 17, 1878) vol. II, p. 471-475.

The Principles of pleading, practice and procedure in civil actions in the High Court of Justice /

Includes bibliographical references.

The world's debate; an historical defence of the allies,

Mode of access: Internet.

Smith's Canadian gazetteer : comprising statistical and general information respecting all parts of the upper province, or Canada West ... With a map of the upper province /

Mode of access: Internet.

Lectures on modern history; from the irruption of the northern nation to the close of the American revolution.

Mode of access: Internet.

Lectures on modern history : from the irruption of the northern nations to the close of the American Revolution /

Title on spine: Professor Smyth's lectures on modern history.