HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 278, Issue 17, 14782-14787, April 25, 2003

This Article Full Text Full Text (PDF) All Versions of this Article: 278/17/14782    most recent M213207200v1 Submit a Letter to Editor 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 Saito, H. Articles by Lund-Katz, S. Search for Related Content PubMed PubMed Citation Articles by Saito, H. Articles by Lund-Katz, S. Social Bookmarking                      What's this?

Characterization of the Heparin Binding Sites in Human Apolipoprotein E^*

Hiroyuki Saito^§, Padmaja Dhanasekaran, David Nguyen, Faye Baldwin, Karl H. Weisgraber^¶, Suzanne Wehrli, Michael C. Phillips, and Sissel Lund-Katz

From the  Joseph Stokes, Jr. Research Institute, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-4318 and the ^¶ Gladstone Institute of Cardiovascular Disease, Cardiovascular Research Institute, and Department of Pathology, University of California, San Francisco, California 94141

Apolipoprotein (apo) E mediates lipoprotein remnant clearance via interaction with cell-surface heparan sulfate proteoglycans. Both the 22-kDa N-terminal domain and 10-kDa C-terminal domain of apoE contain a heparin binding site; the N-terminal site overlaps with the low density lipoprotein receptor binding region and the C-terminal site is undefined. To understand the molecular details of the apoE-heparin interaction, we defined the microenvironments of all 12 lysine residues in intact apoE3 and examined their relative contributions to heparin binding. Nuclear magnetic resonance measurements showed that, in apoE3-dimyristoyl phosphatidylcholine discs, Lys-143 and -146 in the N-terminal domain and Lys-233 in the C-terminal domain have unusually low pK_a values, indicating high positive electrostatic potential around these residues. Binding experiments using heparin-Sepharose gel demonstrated that the lipid-free 10-kDa fragment interacted strongly with heparin and a point mutation K233Q largely abolished the binding, indicating that Lys-233 is involved in heparin binding and that an unusually basic lysine microenvironment is critical for the interaction with heparin. With lipidated apoE3, it is confirmed that the Lys-233 site is completely masked and the N-terminal site mediates heparin binding. In addition, mutations of the two heparin binding sites in intact apoE3 demonstrated the dominant role of the N-terminal site in the heparin binding of apoE even in the lipid-free state. These results suggest that apoE interacts predominately with cell-surface heparan sulfate proteoglycans through the N-terminal binding site. However, Lys-233 may be involved in the binding of apoE to certain cell-surface sites, such as the protein core of biglycan.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				P. S. Bhattacharjee, D. M. Neumann, T. P. Foster, C. Clement, G. Singh, H. W. Thompson, H. E. Kaufman, and J. M. Hill Effective Treatment of Ocular HSK with a Human Apolipoprotein E Mimetic Peptide in a Mouse Eye Model Invest. Ophthalmol. Vis. Sci., October 1, 2008; 49(10): 4263 - 4268. [Abstract] [Full Text] [PDF]

				K. E. Kypreos, K. W. van Dijk, L. M. Havekes, and V. I. Zannis Generation of a Recombinant Apolipoprotein E Variant with Improved Biological Functions: HYDROPHOBIC RESIDUES (LEU-261, TRP-264, PHE-265, LEU-268, VAL-269) OF apoE CAN ACCOUNT FOR THE apoE-INDUCED HYPERTRIGLYCERIDEMIA J. Biol. Chem., February 25, 2005; 280(8): 6276 - 6284. [Abstract] [Full Text] [PDF]

				M. Futamura, P. Dhanasekaran, T. Handa, M. C. Phillips, S. Lund-Katz, and H. Saito Two-step Mechanism of Binding of Apolipoprotein E to Heparin: IMPLICATIONS FOR THE KINETICS OF APOLIPOPROTEIN E-HEPARAN SULFATE PROTEOGLYCAN COMPLEX FORMATION ON CELL SURFACES J. Biol. Chem., February 18, 2005; 280(7): 5414 - 5422. [Abstract] [Full Text] [PDF]

				H. Saito, P. Dhanasekaran, F. Baldwin, K. H. Weisgraber, M. C. Phillips, and S. Lund-Katz Effects of Polymorphism on the Lipid Interaction of Human Apolipoprotein E J. Biol. Chem., October 17, 2003; 278(42): 40723 - 40729. [Abstract] [Full Text] [PDF]