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Srcasm corrects Fyn-induced epidermal hyperplasia by kinase down-regulation
Weijie Li1, Christine Marshall, Lijuan Mei
1Department of Dermatology, University of Pennsylvania Medical School, Philadelphia, Pennsylvania 19104, USA.
The Journal of Biological Chemistry
|October 19, 2006
Summary
Src family tyrosine kinases (SFKs) regulate epithelial growth. Srcasm acts as a rheostat, down-regulating Fyn kinase activity and controlling epithelial hyperproliferation by requiring phosphorylation and the GAT domain.
Area of Science:
- Cell Biology
- Molecular Biology
- Dermatology
Background:
- Src family tyrosine kinases (SFKs) are crucial for epithelial cell growth and differentiation.
- Dysregulated SFK activity contributes to various diseases.
- Understanding SFK regulation is key to disease pathogenesis.
Purpose of the Study:
- To investigate the role of Fyn, an SFK, in epidermal growth and differentiation in vivo.
- To characterize the regulatory mechanism of Fyn activity by Srcasm.
- To explore the potential of Srcasm as a therapeutic target for epithelial hyperproliferation.
Main Methods:
- Generation of Keratin 14-Fyn (K14) transgenic mice to study Fyn's effect on epidermis.
- Derivation of double transgenic K14-Fyn/Srcasm mice to assess Srcasm's in vivo impact on Fyn.
- Biochemical analyses to elucidate the molecular mechanism of Srcasm-mediated Fyn down-regulation.
Main Results:
- K14-Fyn mice exhibited epidermal hyperproliferation and thickening.
- Srcasm expression in K14-Fyn mice resolved the hyperproliferative phenotype.
- A nonphosphorylatable Srcasm mutant failed to rescue hyperproliferation, indicating phosphorylation-dependent regulation.
- Srcasm-dependent Fyn down-regulation requires Fyn kinase activity, Srcasm phosphorylation, and the Srcasm GAT domain.
Conclusions:
- Srcasm acts as a novel, phosphorylation-dependent regulator of Fyn kinase activity.
- Srcasm functions as a molecular rheostat, controlling SFK activity and epithelial hyperproliferation.
- Cellular Srcasm levels are critical for managing epithelial cell growth in conditions of elevated SFK activity.
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