Sequence analysis, tissue distribution, and expression of rat cathepsin S

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Cysteine proteases are crucial for various cellular functions, including protein processing and degradation.
• Identifying novel cysteine proteases is essential for understanding cellular mechanisms.

Purpose of the Study:

• To identify novel cysteine proteases in rat brain.
• To characterize the function and expression of a newly identified protease, rat cathepsin S.

Main Methods:

• Polymerase chain reaction (PCR) amplification using primers for conserved catalytic sites.
• Cloning, sequencing, and homology analysis of amplified DNA fragments.
• Screening of a rat brain cDNA library and nucleotide sequencing.
• Northern blot analysis to determine tissue-specific expression.
• Expression and functional characterization of the purified rat cathepsin S protein.

Main Results:

• Five novel cysteine protease sequences were identified alongside rat cathepsins B and L.
• A novel sequence showed high homology to human cathepsin S, identified as rat cathepsin S.
• Rat cathepsin S exhibits distinct tissue-specific expression compared to cathepsins B and L.
• Thyroid-stimulating hormone significantly increased rat cathepsin S mRNA levels in FRTL-5 cells.
• Expressed rat cathepsin S demonstrated proteolytic activity similar to bovine cathepsin S.

Conclusions:

• Rat cathepsin S represents a novel cysteine protease with specific functions.
• Its expression is regulated by thyroid-stimulating hormone, indicating a role in thyroid function.
• The distinct expression pattern and regulation suggest specialized cellular roles for cathepsin S.