Human cathepsin F. Molecular cloning, functional expression, tissue localization, and enzymatic characterization

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Papain-like cysteine proteases are crucial enzymes involved in various cellular processes.
• Understanding novel cathepsins can elucidate new biological pathways and potential therapeutic targets.

Purpose of the Study:

• To clone and characterize a novel human papain-like cysteine protease, cathepsin F.
• To investigate its expression patterns, enzymatic activity, and cellular localization.

Main Methods:

• cDNA cloning from a skeletal muscle library.
• Sequence analysis and homology comparisons with known cathepsins.
• Northern blot analysis for expression profiling.
• Recombinant protein expression and activity assays.
• Transient expression in COS-7 cells for localization studies.

Main Results:

• Cathepsin F shares 58% homology with cathepsin W and forms a potential new cathepsin subgroup.
• High expression observed in heart, skeletal muscle, brain, and gonads; moderate in other tissues.
• Active mature form exhibits broad pH optimum (5.2-6.8) and low pH stability.
• Demonstrates a signal peptide-independent lysosomal targeting pathway, unlike other cathepsins.

Conclusions:

• Cathepsin F is a novel human cysteine protease with distinct expression and localization characteristics.
• Its unique targeting mechanism suggests specialized functions, potentially in acidic cellular compartments.
• Further research into cathepsin F could reveal new insights into protease biology and disease.