The ankyrin-binding domain of CD44s is involved in regulating hyaluronic acid-mediated functions and prostate tumor cell transformation.
CD44 isoforms, such as CD44s (the standard form), contain at least one ankyrin-binding site within the 70-amino acid (aa) cytoplasmic domain and several hyaluronic acid (HA)-binding sites within the extracellular domain. To study the role of CD44s-ankyrin interaction in regulating human prostate tumor cells, we have constructed several CD44s cytoplasmic deletion mutants that lack the ankyrin-binding site(s). These truncated cDNAs were stably transfected into CD44-negative human prostate tumor cells (LNCaP). Our results indicate that a critical region of 15-amino acids (aa) between aa 304 and aa 318 of CD44s is required for ankyrin binding. Biochemical analyses, using competition binding assays with a synthetic peptide containing the 15 aa between aa 304 and aa 318 (NSGNGAVEDRKPSGL), further support the conclusion that this region contains the ankyrin-binding domain of CD44s. Deletion of this 15-aa ankyrin-binding sequence from CD44s results in a drastic reduction of HA-mediated binding/cell adhesion, Src p60 kinase(s) interaction and anchorage-independent growth in soft agar. These findings suggest that the binding of cytoskeletal proteins, such as ankyrin, to the cytoplasmic domain of CD44s plays a pivotal role in regulating HA-mediated functions as well as Src kinase activity and prostate tumor cell transformation.
Zhu
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Department of Cell Biology and Anatomy, University of Miami Medical School, Florida 33101, USA.
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D000595:Amino Acid Sequence; D017487:Ankyrins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D018076:DNA, Complementary; D006801:Humans; D018960:Hyaluronan Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006820:Hyaluronic Acid / Q000378:metabolism*; D008297:Male; D008840:Microfilament Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000503:physiopathology*; D011485:Protein Binding; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D017384:Sequence Deletion; D013049:Spectrin / Q000378:metabolism; D014407:Tumor Cells, Cultured
D017487:Ankyrins; D002352:Carrier Proteins; D018076:DNA, Complementary; D018960:Hyaluronan Receptors; D006820:Hyaluronic Acid; D008840:Microfilament Proteins; D010455:Peptides; D016392:Proto-Oncogene Proteins pp60(c-src); D011993:Recombinant Fusion Proteins; D013049:Spectrin