title: Cilia have high cAMP levels that are inhibited by Sonic Hedgehog-regulated calcium dynamics.
abstract: Protein kinase A (PKA) phosphorylates Gli proteins, acting as a negative regulator of the Hedgehog pathway. PKA was recently detected within the cilium, and PKA activity specifically in cilia regulates Gli processing. Using a cilia-targeted genetically encoded sensor, we found significant basal PKA activity. Using another targeted sensor, we measured basal ciliary cAMP that is fivefold higher than whole-cell cAMP. The elevated basal ciliary cAMP level is a result of adenylyl cyclase 5 and 6 activity that depends on ciliary phosphatidylinositol (3,4,5)-trisphosphate (PIP3), not stimulatory G protein (Gαs), signaling. Sonic Hedgehog (SHH) reduces ciliary cAMP levels, inhibits ciliary PKA activity, and increases Gli1. Remarkably, SHH regulation of ciliary cAMP and downstream signals is not dependent on inhibitory G protein (Gαi/o) signaling but rather Ca2+entry through a Gd3+-sensitive channel. Therefore, PIP3sustains high basal cAMP that maintains PKA activity in cilia and Gli repression. SHH activates Gli by inhibiting cAMP through a G protein-independent mechanism that requires extracellular Ca2+entry.
authors: Department of Molecular and Functional Genomics, Weis Center for Research, Geisinger Clinic, Danville, PA 17822.
authors: Bryn S
authors: BS
authors: Moore
authors: Department of Molecular and Functional Genomics, Weis Center for Research, Geisinger Clinic, Danville, PA 17822.
authors: Ann N
authors: AN
authors: Stepanchick
authors: Montana Molecular, Bozeman, MT 59718.
authors: Paul H
authors: PH
authors: Tewson
authors: Department of Molecular and Functional Genomics, Weis Center for Research, Geisinger Clinic, Danville, PA 17822.
authors: Cassandra M
authors: CM
authors: Hartle
authors: Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093.
authors: Jin
authors: J
authors: Zhang
authors: Montana Molecular, Bozeman, MT 59718.
authors: Anne Marie
authors: AM
authors: Quinn
authors: Montana Molecular, Bozeman, MT 59718.
authors: Thomas E
authors: TE
authors: Hughes
authors: Department of Molecular and Functional Genomics, Weis Center for Research, Geisinger Clinic, Danville, PA 17822; tmirshahi@geisinger.edu.
authors: Tooraj
authors: T
authors: Mirshahi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D002923:Cilia / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D053823:Hedgehog Proteins / Q000378:metabolism*; D051379:Mice; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*
chemical_list: D053823:Hedgehog Proteins; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium
keywords: Hedgehog; PIP3; PKA; cAMP; cilia