Protein tyrosyl phosphatase-1B is expressed by normal human epidermis, keratinocytes, and A-431 cells and dephosphorylates substrates of the epidermal growth factor receptor.
In the epidermis tyrosine kinases such as those found in the epidermal growth factor receptor (EGF-R) phosphorylate regulatory molecules on tyrosine and play an important role in controlling epidermal growth. Phosphotyrosyl phosphatases (PTPase) that dephosphorylate EGF-R and other proteins phosphorylated on tyrosine must also play an important role in controlling epidermal growth. The presence and metabolism of one such PTPase, PTP-1B, was detected and studied in human skin using biochemical, immunochemical, and molecular biologic methods. The message for PTP-1B was expressed in human epidermis, in keratinocytes cultured from human epidermis, and in human keratinocyte cell lines. The 49-kDa but not the 37-kDa form of PTP-1B was identified in membranes prepared from these cells and tissues by immunodetection on Western blots. Nearly all of the labeled proteins identified by gel electrophoresis of an A-431 particulate fraction phosphorylated with [gamma-32P] ATP in the presence of epidermal growth factor are substrates for PTP-1B because their labeling decreased after incubation with a catalytically active and purified PTP-1B fusion protein. Immunohistochemical methods were used to show that PTP-1B was primarily localized to the basal cell layers in normal thick epidermis. The presence of PTP-1B in intact human epidermis suggests that this molecule is not an artifact limited to cultured cells but is an important molecule in the in vivo regulation of epidermal functions.
Department of Medicine, Vanderbilt University, Nashville, Tennessee.
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P
Gunaratne
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Stoscheck
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Gates
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Li
L B
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Nanney
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King
D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D004817:Epidermis / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000378:metabolism*; D008970:Molecular Weight; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012016:Reference Values; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D066246:ErbB Receptors; D017027:Protein Tyrosine Phosphatases