Alternative splicing of CHI3L1 regulates protein secretion through conformational changes

Area of Science:

• Molecular Biology
• Post-transcriptional Regulation
• Protein Isoform Diversity

Background:

• Alternative splicing (AS) generates protein isoforms with diverse functions.
• Chitinase 3-like 1 (CHI3L1) is implicated in various biological processes.
• Understanding CHI3L1 regulation is crucial for its role in disease.

Purpose of the Study:

• To identify and characterize a novel alternative splicing event in CHI3L1.
• To investigate how this splicing event impacts CHI3L1 protein secretion.
• To elucidate the conformational changes associated with CHI3L1 alternative splicing.

Main Methods:

• Analysis of GTEx dataset for tissue-specific CHI3L1 splicing.
• RT-PCR to study CHI3L1 splicing regulation in THP-1 and BEAS-2B cells.
• AlphaFold for structural modeling of CHI3L1 isoforms.
• Western blotting to assess protein expression and secretion.

Main Results:

• CHI3L1 exon 8 exclusion is tissue-specific, notably in lung tissue.
• CHI3L1 splicing is dynamically regulated by cellular context (macrophage differentiation, cell density).
• Exon 8 exclusion alters CHI3L1 conformation, impairing signal peptide orientation and reducing secretion.

Conclusions:

• Alternative splicing-mediated exclusion of CHI3L1 exon 8 is a novel mechanism controlling protein secretion.
• Conformational changes induced by AS regulate CHI3L1 secretion.
• This study provides new insights into post-transcriptional regulation of secreted proteins.