Reactome: A Curated Pathway Database

SMURF1/2 bind PTCH1

Stable Identifier
Homo sapiens
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Hh stimulation promotes PTCH1 clearance from the primary cilium to endocytic compartments (Rohatgi et al, 2007; reviewed in Nowaza et al, 2013). Receptor internalization is required for pathway activation, and additionally limits the duration and range of Hh signaling by sequestering the ligand inside the cell (Rohatgi et al, 2007; Incardona et al, 2000; Incardona et al, 2002; Denef et al, 2000; Huang et al, 2013; Yue et al, 2014). Upon Hh pathway activation, the E3 ligases SMURF1 and SMURF2 bind to two PPXY motifs in the C-terminal tail of PTCH1 to promote its ubiquination, endocytosis and degradation. In Drosophila, SMURF-mediated ubiquitination of PTCH is depends on an interaction between SMURF and activated SMO, but this does not appear to be true in vertebrates where PTCH1 turnover is SMO-independent (Yue et al, 2014; Huang et al, 2013; Lu et al, 2006). In flies, SMURF-dependent ubiquitination preferentially downregulates ligand-unbound receptor and is thus believed to regulate downstream signaling by altering the ratio of bound to unbound receptor on the cell surface; this aspect of PTCH1 downregulation has not been examined in detail in vertebrate cells (Huang et al, 2013; Casali and Struhl, 2004; Yue et al, 2014).

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