Hedgehog Signaling

The hedgehog (Hh) cell signaling pathway promotes cell growth and differentiation during embryonic development. Hh signaling is frequently aberrantly activated in cancer. The Hh signaling pathway may be activated by hedgehog ligands (sonic, desert, indian) binding to PTCH1 on the cell surface. In the absence of a hedgehog ligand, the Hh pathway is inhibited by PTCH1. PTCH1 inhibits the activation of SMO by maintaining SMO inside a vesicle within the cell.

Figure 1. In the absence of hedgehog ligands, patched (PTCH1) is an inhibitory receptor that inhibits hedgehog signaling by maintaining the activating receptor smoothened (SMO) within a vesicle inside the cell. The binding of hedgehog ligands (sonic, desert, and indian) bind to PTCH1 releases PTCH1 from SMO and causes PTCH1 to be internalized and degraded. SMO migrates to the cell surface and initiates hedgehog signaling. The activation of SMO causes gene transcription and promotes normal embryonic development as well as cell growth and survival. Specific nodes in the pathway that are therapeutically actionable are noted. Click here to open a larger version of this image in a new window.

Downstream Pathways

Cell cycle control

Diseases in Which Pathway is Aberrantly Activated

Therapies That Target This Pathway

SMO inhibitors

Genes Involved in the Pathway

Last Updated: May 24, 2016

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