This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Castellani, L. W. Articles by Lusis, A. J. Search for Related Content PubMed PubMed Citation Articles by Castellani, L. W. Articles by Lusis, A. J.

(Arteriosclerosis, Thrombosis, and Vascular Biology. 2001;21:1870.)
© 2001 American Heart Association, Inc.

Editorials

ApoA-II Versus ApoA-I

Two for One Is Not Always a Good Deal

Lawrence W. Castellani; Aldons J. Lusis

Departments of Medicine (L.W.C., A.J.L.) and Microbiology (A.J.L.), Immunology and Molecular Genetics, and Molecular Biology Institute (A.J.L.), University of California, Los Angeles.

Correspondence to Lawrence W. Castellani, PhD, Department of Medicine/Division of Cardiology, 47-123 CHS, University of California, Los Angeles, CA 90095. E-mail lcastellani@mednet.ucla.edu

Apolipoprotein A-I (apoA-I), the major protein of HDL, is probably among the most intensively studied of all proteins. It functions in HDL assembly, in the removal of excess cholesterol from cells, and in the transport of cholesterol from peripheral tissues to the liver, a process known as "reverse cholesterol transport." It is a cofactor for lecithin:cholesterol acyl transferase (LCAT), the enzyme responsible for cholesterol esterification in HDL, and it stabilizes certain antioxidant enzymes, such as serum paraoxonase, that are carried on HDL.^1,2 Rare null mutations of apoA-I in human populations are associated with early coronary heart disease,³ and overexpression of apoA-I in transgenic mice protects against atherogenesis.⁴ An exciting recent development was the 4-angstrom-resolution x-ray structure for the helical part of apoA-I, encompassing residues 44 to 243 (reviewed by Segrest et al⁵).

See page 1977

In contrast, apolipoprotein A-II (apoA-II), the second most abundant protein of HDL, has no known function, and it has been the subject of few detailed studies. Its presence in HDL has been reported to decrease,⁶ or have no influence on, cholesterol efflux from cells,^7,8 nor is it a cofactor for any known enzyme. Rare individuals lacking apoA-II appear to have normal plasma lipids.⁹ In fact, all of the known effects of apoA-II are deleterious. In studies with mice and humans, apoA-II levels have been associated with increased susceptibility to atherosclerosis,^10–13 increased free fatty acid levels,^14,15 increased body fat,^15,16 and increased insulin resistance.^15,17 Undoubtedly, apoA-II has some unknown beneficial functions, possibly related to fatty acid . . . [Full Text of this Article]

This article has been cited by other articles:

				H. Allayee, A. Ghazalpour, and A. J. Lusis Using Mice to Dissect Genetic Factors in Atherosclerosis Arterioscler Thromb Vasc Biol, September 1, 2003; 23(9): 1501 - 1509. [Abstract] [Full Text] [PDF]

				F. Parhami, B. Basseri, J. Hwang, Y. Tintut, and L. L. Demer High-Density Lipoprotein Regulates Calcification of Vascular Cells Circ. Res., October 4, 2002; 91(7): 570 - 576. [Abstract] [Full Text] [PDF]

				B. G. Brown, M. C. Cheung, A. C. Lee, X.-Q. Zhao, and A. Chait Antioxidant Vitamins and Lipid Therapy: End of a Long Romance? Arterioscler Thromb Vasc Biol, October 1, 2002; 22(10): 1535 - 1546. [Abstract] [Full Text] [PDF]