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EGF-induced ERK phosphorylation independent of PKC isozymes in human corneal epithelial cells.
Invest Ophthalmol Vis Sci. 2002 Dec; 43(12):3673-9.IO

Abstract

PURPOSE

To investigate the role of protein kinase C (PKC) isozymes in epithelial growth factor (EGF)-induced activation of extracellular signal-regulated kinase (ERK) and cell proliferation in cultured human corneal epithelial cells.

METHODS

Simian virus (SV)40 stably transfected human corneal epithelial (THCE) cells were cultured in keratinocyte growth medium. PKC isozymes and phosphorylation of ERK in THCE cells were assessed by Western blot analysis. Translocation of the PKC isozyme was determined by subcellular fractionation followed by Western blot analysis. Cell proliferation was measured by incorporation of [(3)H]-thymidine into DNA.

RESULTS

Six PKC isozymes-PKC-alpha, -betaI, -betaII, -delta, - epsilon, and - micro -were found in THCE cells. Phorbol 12-myristate 13-acetate (PMA) caused PKC-alpha, -betaI, and - epsilon, initially present in the cytoplasm, to be translocated to the membrane and nuclear subcellular fractions and PKC-delta to be depleted from the cytoskeleton. The PKC inhibitor GF109203X inhibited PMA-induced, but not basal or EGF-induced, phosphorylation of ERK, whereas the EGF receptor inhibitor tyrphostin AG1478 blocked basal and EGF-, but not PMA-, induced phosphorylation of ERK. Depletion of PMA-sensitive PKC isozymes including PKC-alpha, -betaI, -betaII, -delta, and - epsilon, inhibited PMA-, but not EGF-, induced phosphorylation of ERK. Depletion of these PKC isozymes blocked PMA-, but not EGF-, induced cell proliferation.

CONCLUSIONS

Although activation of PKC by PMA results in activation of ERK, EGF-induced phosphorylation of ERK and/or cell proliferation is independent of the conventional and novel isozymes PKC-alpha, -betaI, -betaII, -delta, and - epsilon in human corneal epithelial cells.

Authors+Show Affiliations

Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta 30912, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

12454035

Citation

Xu, Ke-Ping, et al. "EGF-induced ERK Phosphorylation Independent of PKC Isozymes in Human Corneal Epithelial Cells." Investigative Ophthalmology & Visual Science, vol. 43, no. 12, 2002, pp. 3673-9.
Xu KP, Dartt DA, Yu FS. EGF-induced ERK phosphorylation independent of PKC isozymes in human corneal epithelial cells. Invest Ophthalmol Vis Sci. 2002;43(12):3673-9.
Xu, K. P., Dartt, D. A., & Yu, F. S. (2002). EGF-induced ERK phosphorylation independent of PKC isozymes in human corneal epithelial cells. Investigative Ophthalmology & Visual Science, 43(12), 3673-9.
Xu KP, Dartt DA, Yu FS. EGF-induced ERK Phosphorylation Independent of PKC Isozymes in Human Corneal Epithelial Cells. Invest Ophthalmol Vis Sci. 2002;43(12):3673-9. PubMed PMID: 12454035.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - EGF-induced ERK phosphorylation independent of PKC isozymes in human corneal epithelial cells. AU - Xu,Ke-Ping, AU - Dartt,Darlene A, AU - Yu,Fu-Shin X, PY - 2002/11/28/pubmed PY - 2002/12/13/medline PY - 2002/11/28/entrez SP - 3673 EP - 9 JF - Investigative ophthalmology & visual science JO - Invest. Ophthalmol. Vis. Sci. VL - 43 IS - 12 N2 - PURPOSE: To investigate the role of protein kinase C (PKC) isozymes in epithelial growth factor (EGF)-induced activation of extracellular signal-regulated kinase (ERK) and cell proliferation in cultured human corneal epithelial cells. METHODS: Simian virus (SV)40 stably transfected human corneal epithelial (THCE) cells were cultured in keratinocyte growth medium. PKC isozymes and phosphorylation of ERK in THCE cells were assessed by Western blot analysis. Translocation of the PKC isozyme was determined by subcellular fractionation followed by Western blot analysis. Cell proliferation was measured by incorporation of [(3)H]-thymidine into DNA. RESULTS: Six PKC isozymes-PKC-alpha, -betaI, -betaII, -delta, - epsilon, and - micro -were found in THCE cells. Phorbol 12-myristate 13-acetate (PMA) caused PKC-alpha, -betaI, and - epsilon, initially present in the cytoplasm, to be translocated to the membrane and nuclear subcellular fractions and PKC-delta to be depleted from the cytoskeleton. The PKC inhibitor GF109203X inhibited PMA-induced, but not basal or EGF-induced, phosphorylation of ERK, whereas the EGF receptor inhibitor tyrphostin AG1478 blocked basal and EGF-, but not PMA-, induced phosphorylation of ERK. Depletion of PMA-sensitive PKC isozymes including PKC-alpha, -betaI, -betaII, -delta, and - epsilon, inhibited PMA-, but not EGF-, induced phosphorylation of ERK. Depletion of these PKC isozymes blocked PMA-, but not EGF-, induced cell proliferation. CONCLUSIONS: Although activation of PKC by PMA results in activation of ERK, EGF-induced phosphorylation of ERK and/or cell proliferation is independent of the conventional and novel isozymes PKC-alpha, -betaI, -betaII, -delta, and - epsilon in human corneal epithelial cells. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/12454035/EGF_induced_ERK_phosphorylation_independent_of_PKC_isozymes_in_human_corneal_epithelial_cells_ L2 - http://iovs.arvojournals.org/article.aspx?volume=43&page=3673 DB - PRIME DP - Unbound Medicine ER -