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Isolation of a cDNA encoding a tyrosine kinase expressed in murine skin
Y Kawachi1, H Nakauchi, F Otsuka
1Department of Dermatology, University of Tsukuba, Japan.
Abstract:
Tyrosine phosphorylation is widely recognized as playing an important role in cell differentiation, proliferation and carcinogenesis. We used the polymerase chain reaction (PCR) method to identify protein tyrosine kinases that were expressed in the skin. Mixed oligonucleotide probes were used to amplify and screen neonatal murine skin mRNA for clones encoding amino acid contiguities, the conservation of which is characteristic of the protein tyrosine kinase family. When the PCR products were sequenced, a novel clone encoding protein tyrosine kinase, PTK70, was identified. A full-length cDNA was isolated from a mouse thymus cDNA library. The nucleotide and deduced amino acid sequence showed that it featured src-homology (SH) 2 domain, SH3 domain and kinase domain like other src family protein tyrosine kinases, but lacked the N-terminal myristylation site and C-terminal tyrosine residue. Although the mRNA of PTK70 was detected in various tissues ubiquitously, the degree of its expression differed among tissues. Murine skin is one in which PTK70 was expressed strongly, with its expression being much stronger in the epidermis and in the cell line derived from murine keratinocytes than in those from melanoma or fibroblast cell lines. These evidences suggest that PTK70 may be involved in proliferation or differentiation of keratinocytes in the skin.
Insights
Researchers identified a novel protein tyrosine kinase, PTK70, in mouse skin. This protein kinase is highly expressed in skin keratinocytes, suggesting a role in skin cell proliferation and differentiation.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Tyrosine phosphorylation is crucial for cell differentiation, proliferation, and carcinogenesis.
- Protein tyrosine kinases (PTKs) are key regulators of cellular signaling pathways.
Purpose of the Study:
- To identify novel protein tyrosine kinases expressed in murine skin.
- To characterize the expression pattern and potential function of a newly identified PTK, PTK70.
Main Methods:
- Polymerase chain reaction (PCR) was used to screen neonatal murine skin mRNA.
- Mixed oligonucleotide probes were employed to amplify PTK family members.
- Sequencing of PCR products and isolation of full-length cDNA from a mouse thymus library.
- Analysis of nucleotide and amino acid sequences, including domain identification.
Main Results:
- A novel PTK clone, PTK70, was identified in murine skin.
- PTK70 possesses SH2, SH3, and kinase domains, characteristic of src family PTKs, but lacks a myristylation site and C-terminal tyrosine.
- PTK70 mRNA is ubiquitously expressed but shows strong expression in murine skin, particularly in epidermis and keratinocyte cell lines.
- Expression levels were significantly higher in keratinocytes compared to melanoma or fibroblast cell lines.
Conclusions:
- PTK70 is a novel src family-like protein tyrosine kinase identified in murine skin.
- The distinct structural features and strong expression in skin keratinocytes suggest PTK70 plays a role in keratinocyte proliferation or differentiation.
- Further investigation into PTK70's function is warranted to understand its role in skin biology and potential involvement in skin-related diseases.