Wn mutation of c-kit receptor affects its post-translational processing and extracellular expression
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U Koshimizu1, T Tsujimura, K Isozaki
1Research Institute for Microbial Diseases, Osaka University, Japan.
Abstract:
The W locus of mice encodes the c-kit receptor tyrosine kinase. Recently, we characterized a novel mutant allele, Wn, and demonstrated that the c-kit protein synthesized in Wn/Wn cultured mast cells (CMC) was reduced in size and not expressed on their surface (Tsujimura et al., 1993). In this study, we further examined biochemical nature of the mutant form of c-kit protein, by using Wn/Wn CMC and 293T cells transfected with Wn-type c-kit cDNA (c-kitWn). The c-kit product synthesized in Wn/Wn CMC was truncated almost all cytoplasmic domain and was less glycosylated. In c-kitWn-transected cells, both glycosylation and extracellular expression of c-kit protein was also impaired, however, no truncation was detected. These results indicate that Wn-mutant form of c-kit product is insufficient in maturation, which is associated with impairments in the transport to the plasma membrane, and retention of the mutant protein in endoplasmic reticulum is suggested. This is the first demonstration of the c-kit mutation affecting posttranslational processing its product.
Insights
The Wn mutation in mice affects c-kit protein maturation, causing truncation and impaired transport. This novel c-kit mutation impacts post-translational processing and cell surface expression.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The W locus in mice encodes the c-kit receptor tyrosine kinase, crucial for various cellular functions.
- A novel mutant allele, Wn, results in c-kit protein with reduced size and surface expression in cultured mast cells (CMC).
Purpose of the Study:
- To investigate the biochemical characteristics of the Wn-mutant c-kit protein.
- To understand the impact of the Wn mutation on c-kit protein processing and localization.
Main Methods:
- Biochemical analysis of c-kit protein from Wn/Wn CMC.
- Expression studies using 293T cells transfected with Wn-type c-kit cDNA (c-kitWn).
Main Results:
- The c-kit product in Wn/Wn CMC exhibited truncation of the cytoplasmic domain and reduced glycosylation.
- Transfected cells expressing c-kitWn showed impaired glycosylation and extracellular expression, but no truncation.
- These findings suggest defective post-translational processing and endoplasmic reticulum retention of the Wn-mutant c-kit protein.
Conclusions:
- The Wn mutation impairs c-kit protein maturation, affecting its transport to the plasma membrane.
- This study provides the first evidence of a c-kit mutation influencing post-translational processing of its product.