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O-linked glycosylation modifies CD44 adhesion to hyaluronate in colon carcinoma cells
A Dasgupta1, K Takahashi, M Cutler
1Division of Medical Oncology, Massachusetts General Hospital, Boston, USA.
Abstract:
CD44 alternative splicing patterns differ between normal and malignant tissue, and accordingly, modulation of CD44 splicing has received the most attention in studies that have examined the role of CD44 in tumor progression. Many investigators have examined functional differences between individual CD44 alternative splice variants. However, specific CD44 isoforms function uniquely depending on the type of cell on which they are expressed, thereby suggesting that additional tissue-specific mechanisms regulate CD44 function. In the present study we have demonstrated that colon carcinoma cells modify CD44 with O-linked glycosyl groups, and blockade of this glycosylation enhances their CD44-mediated adhesion to hyaluronate. This enhancement is attributable principally to CD44H (CD44s) rather than high molecular weight CD44 variants. Use of site-directed mutant CD44H cDNA transfectants demonstrated that CD44 O-linked glycosylation modulates interaction between hyaluronate and the B loop domain of CD44. The influence of glycosylation on CD44 function in colon carcinoma cells is specific to the presence of O-linked sugars; inhibition of N-linked glycosylation had minimal influence on CD44 function. These findings indicate that O-linked glycosylation may be as important as alternative splicing in the regulation of CD44 function and the broad spectrum of biological processes attributed to it, including normal development, tumor metastases, and lymphocyte function.
Insights
O-linked glycosylation of CD44 in colon carcinoma cells enhances adhesion to hyaluronate, suggesting it is as crucial as alternative splicing in regulating CD44 function.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- CD44 alternative splicing varies between normal and malignant tissues, influencing tumor progression.
- Individual CD44 splice variants have distinct functions, but cell-specific regulation is key.
- Tissue-specific mechanisms beyond splicing likely control CD44 function.
Purpose of the Study:
- To investigate the role of CD44 glycosylation in colon carcinoma cells.
- To determine how O-linked glycosylation affects CD44-mediated adhesion to hyaluronate.
- To compare the impact of O-linked versus N-linked glycosylation on CD44 function.
Main Methods:
- Studied CD44 glycosylation in colon carcinoma cells.
- Blocked O-linked glycosylation and assessed CD44-hyaluronate adhesion.
- Utilized site-directed mutant CD44H cDNA transfectants.
- Inhibited N-linked glycosylation to compare effects.
Main Results:
- Colon carcinoma cells O-glycosylate CD44, and blocking this enhances CD44-hyaluronate adhesion.
- Enhanced adhesion is primarily due to CD44H (CD44s), not high molecular weight variants.
- O-linked glycosylation specifically modulates the interaction between hyaluronate and the CD44 B loop domain.
- N-linked glycosylation inhibition had minimal impact on CD44 function.
Conclusions:
- O-linked glycosylation is a significant regulator of CD44 function in colon carcinoma.
- Glycosylation may be as important as alternative splicing in controlling CD44's diverse roles.
- Findings impact understanding of CD44 in tumor metastasis and lymphocyte function.