Molecular Characterization of a Novel Intracellular Hyaluronan-binding Protein

Hyaluronan has well defined functions in extracellular matrices and at the surface of cells. However, several studies have now shown that significant pools of hyaluronan are also present intracellularly, but its function therein is unknown. One avenue of investigation that may assist in defining the...

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Published in:The Journal of biological chemistry 2000-09, Vol.275 (38), p.29829-29839
Main Authors: Huang, Lei, Grammatikakis, Nicholas, Yoneda, Masahiko, Banerjee, Shib D., Toole, Bryan P.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Base Sequence
Chick Embryo
Cloning, Molecular
Cytoplasm
Humans
Hyaluronan Receptors - analysis
Hyaluronan Receptors - genetics
Hyaluronan Receptors - metabolism
Hyaluronic Acid - metabolism
Mice
Molecular Sequence Data
Protein Binding
Sequence Analysis
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Summary:Hyaluronan has well defined functions in extracellular matrices and at the surface of cells. However, several studies have now shown that significant pools of hyaluronan are also present intracellularly, but its function therein is unknown. One avenue of investigation that may assist in defining the function of intracellular hyaluronan is to identify intracellular hyaluronan-binding proteins. In previous studies we identified CDC37, a cell cycle regulatory protein, using a monoclonal antibody that recognizes a novel group of hyaluronan-binding proteins. In this study, we have identified a second hyaluronan-binding protein with this antibody and characterized its properties. This protein, which we have termed IHABP4, was also found to be an intracellular and a specific hyaluronan-binding protein, containing several hyaluronan-binding motifs: (R/K)X7(R/K) (where R/K denotes arginine or lysine and X denotes non-acidic amino acids). Furthermore, we have determined the gene organization ofIHABP4 and cloned cDNAs for the chick, mouse, and human homologs. Comparison of the deduced chick, mouse, and human protein sequences showed that the hyaluronan-binding motifs, (R/K)X7(R/K), in these sequences are conserved; both chick and mouse IHABP4 were shown directly to bind hyaluronan. Biochemical fractionation and immunofluorescent localization of epitope-tagged IHABP4 indicated that it is mainly present in the cytoplasm. These data support the possibility that intracellular hyaluronan and its binding proteins may play important roles in cell behavior.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M002737200