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Cloning and functional expression of a novel endoprotease involved in prohormone processing at dibasic sites
K Nakayama1, M Hosaka, K Hatsuzawa
1Institute of Biological Sciences, University of Tsukuba, Ibaraki.
Abstract:
We cloned and sequenced a cDNA from a library of mouse pituitary AtT-20 cells which are known to cleave an endogenous and various foreign prohormones at dibasic sites. This cDNA encodes a novel 753-residue protein, named PC3, which is structurally related to the yeast Kex2 protease involved in precursor cleavage at dibasic sites and to recently identified mammalian Kex2-like proteins, furin and PC2. Among examined cell lines and tissues, PC3 mRNA was only detected in AtT-20 cells. The substrate specificity of PC3 expressed in mammalian cells was similar to that observed in AtT-20 cells. We conclude that PC3 is a resident prohormone processing endoprotease in AtT-20 cells.
Insights
Researchers identified PC3, a novel proteinase in mouse pituitary cells, crucial for processing prohormones at specific sites. This finding advances understanding of protein maturation in endocrine cells.
Area of Science:
- Molecular Biology
- Endocrinology
- Protease Research
Background:
- Mouse pituitary AtT-20 cells are known for cleaving prohormones at dibasic sites.
- Understanding the enzymes responsible for this post-translational modification is crucial for endocrine research.
Purpose of the Study:
- To identify and characterize novel proteins involved in prohormone processing in AtT-20 cells.
- To determine the specific role and localization of the newly discovered protein PC3.
Main Methods:
- Cloning and sequencing of a cDNA library from mouse pituitary AtT-20 cells.
- Expression of the novel protein (PC3) in mammalian cells to assess substrate specificity.
- Analysis of PC3 mRNA distribution across various cell lines and tissues.
Main Results:
- A novel cDNA encoding a 753-residue protein, named PC3, was identified.
- PC3 shows structural similarity to yeast Kex2 protease and mammalian furin and PC2.
- PC3 mRNA was exclusively detected in AtT-20 cells, and its substrate specificity matched that observed in these cells.
Conclusions:
- PC3 is a novel endoprotease specifically involved in prohormone processing.
- PC3 functions as a resident prohormone processing enzyme within AtT-20 cells.
- The discovery of PC3 contributes to the understanding of mammalian prohormone maturation pathways.