When there is a hedgehog signal, the protein binds to Ptc and its co-receptor iHog (single-pass, called CDO or CDON in mammals) and induces the endocytosis of Patched; this stops the inhibition on Smo.
When there is a hedgehog signal, the protein binds to Ptc and its co-receptor iHog. The binding of HhN to Ptc and iHog induces the endocytosis of Patched; this stops the inhibition on Smo.