An essential embryonic signaling cascade that regulates stem cell and progenitor cell differentiation in multiple developmental processes (Ingham PW).
It is activated by smoothened homologue (SMO) a transmembrane protein.
Smoothened homologue is inhibited by PTCH1 an inhibitory cell surface receptor thereby suppressing activation of the hedgehog pathway.
Hedgehog ligands can bind to and subsequently inactivate PTCH1 decreasing smoothened homologue activity and promoting the hedgehog pathway.