Endogenous Peptide Derived from c-Cbl-Associated Protein Counteracts Its Inhibitory Effect on Enteric Neural Crest Cell Colonization in Hirschsprung Disease.

Hirschsprung disease (HSCR) is a congenital malformation characterized by the absence of the enteric nervous system (ENS) in the distal colon, resulting from defective colonization of enteric neural crest cells (ENCCs). The underlying pathogenesis of HSCR remains incompletely understood. Here, we report that c-Cbl-associated protein (CAP), also known as sorbin and SH3 domain-containing protein 1 (SORBS1), is upregulated in the aganglionic colon tissues of children with HSCR. Functional studies revealed that CAP overexpression suppresses ENCC colonization by binding the lipid raft protein flotillin-1 through its sorbin-homology (SoHo) domain, followed by recruitment of the focal adhesion protein vinculin via its SH3 domain. Using mass spectrometry, we identified an endogenous CAP-derived peptide, termed PDCAP, in aganglionic colon tissues. ELISA further revealed reduced PDCAP levels in the diseased colon tissues of HSCR children. Mechanistically, PDCAP exerts a protective role by competing with its precursor protein, CAP, for binding to flotillin-1, thereby reversing CAP-mediated inhibition of ENCC colonization. This protective function was further validated in Caplsl/lsl;Nestin-Cre as well as Ednrb-/- mouse models of either sex, where PDCAP promoted ENCC colonization and ENS development. Collectively, our findings establish PDCAP as a functional antagonist of its precursor CAP, providing a rationale for exploring peptide-mediated interventions in HSCR.