In autocrine signaling,signal acts on same cells which produce them
Sonic Hedgehog helps in cell growth and development
Hedgehog signaling pathway plays an essential role during vertebrate embryonic development
Sonic hedgehog has particularly marked roles in nervous system cell type specification and limbs patterning
Activation of sonic hedgehog pathway can happen in two major ways:
Canonical signaling: by ligand-dependent interaction or through receptor-induced signaling
Non-canonical signaling:when there’s a mechanism of activation downstream of smoothened
The sonic hedgehog canonical signaling occurs when the glycoprotein sonic hedgehog binds and inactivates the 12-transmembrane protein Patched
In the lack of the ligand sonic hedgehog, the activity of the 7-transmembrane protein smoothened is inhibited by patched so sonic hedgehog protein binding patched regulates smoothened activity
The non–canonical activation occurs through Gli-independent mechanisms and it can be of two types
Type I which modulates Ca2+ and actin cytoskeleton
When sonic hedgehog binds the receptor patched, smoothened is no longer inhibited and couple Gi proteins (G) and small GTPases RhoA and Rac1 activated
Type II is the one which is independent on smoothened
When smoothened binds patched, the interaction of patched with cyclin B1 is disrupted, leading to an increase in cell proliferation and survival
Pupillary response is a physiological response that varies the size of the pupil, via the optic and oculomotor cranial nerve. Involuntary reflex reaction to exposure or inexposure to light—in low light conditions a dilated pupil lets more light into the eye. :)
