Clathrin light chains' role in selective endocytosis influences antibody isotype switching

Area of Science:

• Cell Biology
• Immunology
• Molecular Biology

Background:

• Clathrin, a protein complex, forms vesicle coats essential for endocytosis.
• Clathrin light chains (CLCs) are subunits of clathrin, but their in vivo function remains largely uncharacterized.
• Receptor-mediated endocytosis regulates various cellular processes, including immune responses.

Purpose of the Study:

• To investigate the in vivo function of clathrin light chains (CLCs) in B lymphocytes.
• To determine the role of CLCs in receptor-mediated endocytosis and immune cell regulation.
• To identify specific signaling receptors whose uptake is dependent on CLCs.

Main Methods:

• Generation of CLCa-null mice lacking the major CLC isoform in B cells.
• Analysis of B cell populations, germinal center composition, and IgA production in CLCa-null mice.
• Assessment of endocytosis of various signaling receptors (e.g., CXCR4, TGFβR2, δ-opioid receptor) in CLCa-deficient cells.

Main Results:

• CLCa-null mice exhibited reduced B cell numbers in germinal centers and an enrichment of IgA-producing cells.
• Absence of CLCa led to increased transforming growth factor β receptor 2 (TGFβR2) signaling due to impaired endocytosis.
• Internalization of specific receptors, including CXCR4 and the δ-opioid receptor, was selectively affected by CLC deficiency.

Conclusions:

• Clathrin light chains play a significant role in vivo, influencing the cargo selectivity of clathrin-mediated endocytosis.
• CLCs contribute to the regulation of B cell differentiation and IgA production.
• This study highlights a novel function for CLCs in controlling the uptake of a subset of signaling receptors, a role previously attributed solely to adaptor proteins.