The hyaluronan receptor RHAMM/IHABP in astrocytoma cells: expression of a tumor-specific variant and association with microtubules.
Hyaluronan binding to its cellular receptors CD44 and ICAM-1 appears to enhance the malignant behavior of tumors, including astrocytomas. RHAMM/IHABP, another hyaluronan receptor, has been identified in breast carcinoma cells, but its presence in astrocytomas is yet undetermined. Herein, we report that a monoclonal antibody against plectin (a cytoskeletal protein linker) recognizes on Western blots of U-373 MG glioblastoma cells, a 300-kDa band corresponding to plectin and two bands of 86 and 70 kDa. cDNA cloning and Northern blotting reveals that these two bands represent isoforms of RHAMM/IHABP. Sequence comparisons suggest that the plectin monoclonal antibody recognizes RHAMM/IHABP because this protein and plectin share short peptide sequences of similar primary and secondary structure. Western blotting demonstrates that most human astrocytoma tissues and cell lines express the 86- and 70-kDa isoforms of RHAMM/IHABP. Interestingly, the 70-kDa variant is undetectable in normal brain tissues and in primary cultures of astrocytes suggesting that its expression is tumor-specific. Transfection experiments with epitope-tagged RHAMM/IHABP cDNA established that RHAMM/IHABP associates with microtubules in astrocytoma cells, while in normal astrocytes it either co-localizes with microtubules or has a diffuse cytoplasmic distribution. This suggests that RHAMM/IHABP has the capacity to bind to microtubules in normal and transformed astrocytes, and that neoplasia may favor this association.
Zhou
Rixin
R
Department of Cellular Biology and Anatomy, Louisiana State University Medical Center in Shreveport, 71130-39932, USA.
Wu
Xiao
X
Skalli
Omar
O
D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D000911:Antibodies, Monoclonal; D001254:Astrocytoma / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence / Q000235:genetics; D015152:Blotting, Northern; D002478:Cells, Cultured; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014644:Genetic Variation; D006801:Humans; D018960:Hyaluronan Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000276:immunology; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D051190:Plectin; D020033:Protein Isoforms / Q000378:metabolism; D012016:Reference Values; D014162:Transfection
D000911:Antibodies, Monoclonal; D016326:Extracellular Matrix Proteins; D018960:Hyaluronan Receptors; D007381:Intermediate Filament Proteins; C495332:PLEC protein, human; D051190:Plectin; D020033:Protein Isoforms; C098946:hyaluronan-mediated motility receptor