Agrin-induced AChR aggregate formation requires cGMP and aggregate maturation requires activation of cGMP-dependent protein kinase.
Previously, it was demonstrated that agrin acting through the gaseous, signaling molecule, nitric oxide (NO), induces the formation of AChR aggregates on myotubes in culture. Soluble guanylyl cyclase (sGC), which is present at the neuromuscular junction, is a common target of NO. Therefore, we hypothesized that sGC and cGMP are involved in the agrin signaling cascade. Inhibition of sGC hindered AChR aggregation in both agrin- and NO donor-treated cultured myotubes; whereas, a cGMP analogue was able to induce the formation of AChR aggregates on naïve muscle cells. Due to the presence of cyclic GMP-dependent protein kinase (PKG) at the neuromuscular junction, we tested the ability of a PKG inhibitor to alter the agrin signaling cascade. PKG inhibition did not prevent nascent AChR aggregate formation; however, these aggregates were diffuse and composed of numerous microaggregates consistent with incomplete maturation. Thus, we conclude that cGMP is important for the initiation of AChR aggregation, while PKG is involved in the maturation of AChR aggregates.
Jones
Melissa A
MA
Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
Werle
Michael J
MJ
D018171:Agrin / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase; D018482:Muscle, Skeletal / Q000294:innervation; D009469:Neuromuscular Junction / Q000187:drug effects / Q000196:embryology / Q000201:enzymology*; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D011940:Receptor Aggregation / Q000187:drug effects / Q000502:physiology*; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D000071756:Soluble Guanylyl Cyclase
D018171:Agrin; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D011950:Receptors, Cholinergic; D018160:Receptors, Cytoplasmic and Nuclear; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP