Previously we demonstrated that protein phosphorylation was one of the initial signals induced by Epidermal Growth Factor (EGF) binding to its specific receptor-tyrosine kinase (EGF-R) on sensitive cells. To further study EGF-R in normal and abnormal human skin, human keratinocytes and A-431 cells we will: 1) study the role of specific membrane, cytoskeletal and cytoplasmic components in the initial events occurring after EGF binding. Initial studies will focus on two substrates initially described in A- 431 cells, the 80 kDa substrate (ezerin-like) and the 35kDa (p 35, calpactin II, lipocortin I). In EGF responsive and unresponsive keratinocytes EGF-R interaction with cytoskeletal proteins will be examined to determine how they may be involved in EGF-R aggregation, internalization and degradation; 2) study how EGF stimulates and/or regulates glycolysis in human skin, epidermis and keratinocytes. As an extension of 1), we will examine whether specific cytosolic proteins are phosphorylated on tyrosine by EGF-R to mediate EGF induced glycolysis in human epidermis. The mechanisms whereby growth factors (EGF, insulin and TGFs) stimulate lactic acid production in human keratinocytes are also being investigated by immunohistochemical and biochemical methods. Regulation of glycolysis in human epidermis appears to be different from that observed in transformed fibroblasts and normal human liver; 3) determine how internalization and degradation of EGF-R are reversibly regulated in normal and abnormal human skin. The in situ degradation of native EGF-R to the 150 kDa form will be studied to see if calpain (CANP) degradation is physiologically relevant in differentiation. We will examine EGF-R metabolism in psoriasis since EGF-R are reversibly but persistently expressed, PKc and calmodulin are increased, and CANP, p35, etc. have not been studied. to clarify the nature of the reversible EGF-R abnormality in vivo we will study other hyperproliferative skin diseases and psoriatic skin responses to effective agents (UV, tar, steroids, methotrexate) to see if they induce similar responses on CANP, p35, PKc and other Ca2+ and EGF-R related proteins.
Showing the most recent 10 out of 12 publications
