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(Circulation. 2000;101:1227.)
© 2000 American Heart Association, Inc.

Editorials

Heat Shock Protein 47

A Chaperone for the Fibrous Cap?

R. Sanders Williams, MD

From the Departments of Internal Medicine and Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas.

Correspondence to R. Sanders Williams, MD, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, NB11.200, Dallas, TX 75390-8573. E-mail williams@ryburn.swmed.edu

Key Words: Editorials • atherosclerosis • stress

According to The American Heritage College Dictionary,¹ a chaperone is "a guide or companion whose purpose is to ensure propriety or restrict activity."

The term "molecular chaperone" is applied to proteins that control the proper folding of nascent polypeptides into the correct 3D structure (ensure propriety) or maintain polypeptides in an inactive state (restrict activity) until they have been transported to their ultimate intracellular or extracellular destinations and assembled into functional multiprotein complexes.² Many of the proteins that function as molecular chaperones were originally identified as "heat shock proteins" (Hsps), because their abundance increased in cells subjected to thermal stress. Individual members of the extended Hsps are usually identified by reference to their molecular mass (eg, Hsp70, Hsp90, etc). The terminology can be misleading because not all Hsps are heat-inducible, not all chaperones are called Hsps, and diverse forms of cellular stress other than elevated temperature lead to transcriptional and post-transcriptional regulation of chaperone synthesis.

Many of the molecular chaperones of the extended Hsp family are highly conserved across evolution (ie, very similar in bacteria, yeast, and humans) and are expressed in virtually all cell types.³ Such proteins function in fundamental cellular housekeeping activities to maintain homeostasis with respect to protein folding and sorting among intracellular compartments and the assembly of macromolecular complexes. Several of these ubiquitously expressed Hsps also serve cytoprotective functions during metabolic stresses, as was demonstrated by several groups who studied Hsp70 and other Hsps in hypoxic and ischemic cells and tissues.^{4 5 6}

Other molecular chaperones are . . . [Full Text of this Article]

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