|Detection of Human CD44 by Western Blot. Western blot shows lysates of HeLa human cervical epithelial carcinoma cell line, HUVEC human umbilical vein endothelial cells, and PC‑3 human prostate cancer cell line. PVDF membrane was probed with 0.2 µg/mL of Mouse Anti-Human CD44s Pan Specific Monoclonal Antibody (Catalog # MAB7045) followed by HRP-conjugated Anti-Mouse IgG Secondary Antibody (Catalog # HAF007). Specific bands were detected for CD44 at approximately 80 to 100 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 1.|
|Detection of CD44 in Human Blood Lymphocytes by Flow Cytometry. Human peripheral blood lymphocytes were stained with Mouse Anti‑Human CD44s Pan Specific Monoclonal Antibody (Catalog # MAB7045, filled histogram) or isotype control antibody (Catalog # MAB003, open histogram), followed by Allophycocyanin-conjugated Anti-Mouse IgG Secondary Antibody (Catalog # F0101B).|
|CD44 in Human PBMCs. CD44 was detected in immersion fixed human peripheral blood mononuclear cells (PBMCs) using Mouse Anti-Human CD44s Pan Specific Monoclonal Antibody (Catalog # MAB7045) at 10 µg/mL for 3 hours at room temperature. Cells were stained using the NorthernLights™ 557-conjugated Anti-Mouse IgG Secondary Antibody (red; Catalog # NL007) and counterstained with DAPI (blue). Specific staining was localized to cell surfaces. View our protocol for Fluorescent ICC Staining of Non-adherent Cells.|
|CD44 in Human Tonsil. CD44 was detected in immersion fixed paraffin-embedded sections of human tonsil using Mouse Anti‑Human CD44s Pan Specific Monoclonal Antibody (Catalog # MAB7045) at 15 µg/mL overnight at 4 °C. Tissue was stained using the Anti‑Mouse HRP-DAB Cell & Tissue Staining Kit (brown; Catalog # CTS002) and counterstained with hematoxylin (blue). View our protocol for Chromogenic IHC Staining of Paraffin-embedded Tissue Sections.|
CD44 is a ubiquitously expressed protein that is the major receptor for hyaluronan and exerts control over cell growth and migration (1‑3). Human CD44 has a 20 amino acid (aa) signal sequence, an extracellular domain (ECD) with a 100 aa hyaluronan-binding disulfide-stabilized link region and a 325‑530 aa stem region, a 21 aa transmembrane domain, and a 72 aa cytoplasmic domain. Within the stem, ten variably spliced exons (v1‑10, exons 6‑15) produce multiple protein isoforms (1‑3). The standard or hematopoietic form, CD44s or CD44H, does not include the variable segments (1‑3). Cancer aggressiveness and T cell activation have been correlated with expression of specific isoforms (1, 3). With variable N- and O-glycosylation and splicing within the stalk, CD44 can range from 80 to 200 kDa (1). Within the N‑terminal invariant portion of the ECD (aa 21‑220), human CD44 shares 76%, 76%, 86%, 83% and 79% identity with corresponding mouse, rat, equine, canine and bovine CD44, respectively. The many reported functions of CD44 fall within three categories (1). First, CD44 binds hyaluronan and other ligands within the extracellular matrix and can function as a “platform” for growth factors and metalloproteinases. Second, CD44 can function as a co‑receptor that modifies activity of receptors including MET and the ERBB family of tyrosine kinases. Third, the CD44 intracellular domain links the plasma membrane to the actin cytoskeleton via the ERM proteins, ezrin, radixin and moesin. CD44 can be synthesized in a soluble form (4) or may be cleaved at multiple sites by either membrane-type matrix metalloproteinases, or ADAM proteases to produce soluble ectodomains (5, 6). The cellular portion may then undergo gamma secretase-dependent intramembrane cleavage to form an A beta -like transmembrane portion and a cytoplasmic signaling portion that affects gene expression (7, 8). These cleavage events are thought to promote metastasis by enhancing tumor cell motility and growth (1, 5).
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