Lysosomal degradation of endocytosed proteins depends on the chloride transport protein ClC-7

Area of Science:

• Cell Biology
• Genetics
• Biochemistry

Background:

• Mutations in ClC-7 (chloride channel 7) or its beta-subunit Ostm1 lead to osteopetrosis and lysosomal storage diseases.
• Previous studies using global knockout mice and cell cultures were limited in elucidating the precise mechanism of lysosomal pathology due to severe phenotypes and lack of storage material.

Purpose of the Study:

• To investigate the cell-autonomous role of ClC-7 in lysosomal pathology using tissue-specific knockout mice.
• To understand the mechanism by which ClC-7 deficiency impacts lysosomal function and protein degradation.

Main Methods:

• Generation and analysis of tissue-specific ClC-7 knockout mice (neurons and renal proximal tubular cells).
• In vivo pulse-chase endocytosis experiments in chimeric mice to compare protein handling in ClC-7-deficient versus normal cells.
• Assessment of lysosomal storage material accumulation and cell death.

Main Results:

• Accumulation of storage material occurs cell-autonomously in ClC-7-deficient neurons and renal proximal tubular cells.
• ClC-7-deficient neurons exhibit significant cell death, and glial activation is localized to affected brain regions.
• In renal proximal tubular cells, endocytosed protein half-life significantly increases in the absence of ClC-7, indicating impaired lysosomal degradation.

Conclusions:

• Lysosomal pathology is a direct, cell-autonomous consequence of ClC-7 disruption.
• ClC-7 plays a crucial role in the degradation of proteins within lysosomes.
• Targeting ClC-7 function may offer therapeutic strategies for lysosomal storage diseases.