Ciliary adenylyl cyclases control the Hedgehog pathway.

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Protein kinase A (PKA) negatively regulates the Hedgehog (Hh) pathway at the cilium base.
• The role of adenylyl cyclases (ACs) in modulating Hh pathway activity is not well understood.

Purpose of the Study:

• To investigate the influence of adenylyl cyclases, specifically AC5 and AC6, on the Hedgehog signaling pathway.
• To determine the localization and function of AC5 and AC6 in cerebellar granular neuron precursors (CGNPs).

Main Methods:

• Assessed expression levels of AC5 and AC6 in CGNPs.
• Utilized overexpression and knockdown techniques to study the effects of AC5 and AC6 on Hh pathway activity.
• Investigated the ciliary localization of AC5 and AC6 using mutation analysis.
• Examined the role of G-protein-coupled receptors (GPCRs) and Gα proteins in regulating AC5/AC6 activity.

Main Results:

• AC5 and AC6 are highly expressed in CGNPs and concentrate in the primary cilium.
• Overexpression of AC5/AC6 represses the Hh pathway, while knockdown activates it.
• A novel ciliary-targeting motif in AC5 is crucial for its ciliary localization and Hh pathway inhibition.
• GPCRs and Gα proteins modulate AC5/AC6 activity, thereby regulating the Hh pathway.

Conclusions:

• AC5 and AC6 are key regulators of the Hh pathway through PKA modulation within the primary cilium.
• Ciliary GPCR signaling converges on AC5 and AC6 to control PKA activity and Hh pathway output.
• These findings elucidate a novel mechanism for Hh pathway regulation in neural development.