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.
Gunaratne
P
P
Department of Medicine, Vanderbilt University, Nashville, Tennessee.
Stoscheck
C
C
Gates
R E
RE
Li
L
L
Nanney
L B
LB
King
L E
LE
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