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

J. Biol. Chem., Vol. 283, Issue 31, 21453-21461, August 1, 2008

This Article Full Text Full Text (PDF) All Versions of this Article: 283/31/21453    most recent M800886200v1 Alert me when this article is cited 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 Google Scholar Articles by Pandey, M. S. Articles by Weigel, P. H. PubMed PubMed Citation Articles by Pandey, M. S. Articles by Weigel, P. H. Social Bookmarking                      What's this?

The Cytoplasmic Domain of the Hyaluronan Receptor for Endocytosis (HARE) Contains Multiple Endocytic Motifs Targeting Coated Pit-mediated Internalization^*

From the Department of Biochemistry and Molecular Biology and the Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190

The hyaluronic acid (HA) receptor for endocytosis (HARE) is the primary scavenger receptor for HA and chondroitin sulfates in mammals. The two human isoforms of HARE (full-length 315-kDa and a 190-kDa proteolytic cleavage product), which are type I single-pass membrane proteins, are highly expressed in sinusoidal endothelial cells of lymph nodes, liver, and spleen. Their identical HARE cytoplasmic domains contain four candidate AP-2/clathrin-mediated endocytic signaling motifs as follows: YSYFRI²⁴⁸⁵, FQHF²⁴⁹⁵, NPLY²⁵¹⁹, and DPF²⁵³⁴ (315-HARE numbering). Stably transfected cells expressing 190-HARE(YSYFRI), 190-HARE(FQHF), or 190-HARE(NPLY) (lacking Motifs 1, 2, or 3) had decreased ¹²⁵I-HA endocytosis rates of 49, 39, and 56%, respectively (relative to wild type). In contrast, 190-HARE(DPF) cells (lacking Motif 4) showed no change in HA endocytic rate. Deletions of motifs 1 and 2 or of 1, 2, and 4 decreased the rate of HA endocytosis by only 41%. Endocytosis was 95% decreased in mutants lacking all four motifs. Cells expressing a 190-HARE(Y2519A) mutant of the NPLY motif retained 85–90% of wild type endocytosis, whereas this mutation in the triple motif deletant decreased endocytosis to 7% of wild type. Tyr in NPLY²⁵¹⁹ is thus important for endocytosis. All HARE mutants showed similar HA binding and degradation of the internalized HA, indicating that altering endocytic motifs did not affect ectodomain binding of HA or targeting of internalized HA to lysosomes. We conclude that, although NPLY may be the most important motif, it functions together with two other endocytic motifs; thus three signal sequences (YSYFRI, FQHF, and NPLY) provide redundancy to mediate coated pit targeting and endocytosis of HARE.

Received for publication, February 1, 2008 , and in revised form, May 8, 2008.

^* This work was supported, in whole or in part, by National Institutes of Health Grant GM69961 from the NIGMS. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed. E-mail: paul-weigel{at}ouhsc.edu.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?