The p38 mitogen-activated protein kinase pathway negatively regulates Ca2+-activated K+ channel trafficking in developing parasympathetic neurons.
The trafficking of large-conductance Ca2+-activated K+ channels (K(Ca)) in chick ciliary ganglion neurons is regulated by growth factors. Here we show that a canonical p38 cascade inhibits K(Ca) trafficking in ciliary ganglion neurons. Two different p38 inhibitors (SB202190 or SB203580) or over-expression of dominant-negative forms of several components of the p38 cascade increased K(Ca) in ciliary neurons. Inhibition of protein synthesis or Golgi processing had no effect on this phenomenon, suggesting that p38 is acting at a distal step of the trafficking pathway. Depolymerization of filamentous actin (F-actin) increased functional expression of K(Ca), whereas stabilization of F-actin inhibited the effect of SB202190 on K(Ca) trafficking. SB202190 also caused an immunochemically detectable increase in K(Ca) on the plasma membrane. Inhibition of p38 decreased the extent of cortical F-actin in ciliary neurons. Macroscopic K(Ca) is suppressed by transforming growth factor (TGF) beta3. Application of TGFbeta3 increased the phosphorylation of p38 in ciliary neurons and increased cortical F-actin. Thus, the p38 signaling cascade endogenously suppresses development of functional K(Ca), in part by stabilizing an F-actin barrier that prevents plasma membrane insertion of functional channel complexes. This cascade also appears to mediate inhibitory effects of TGFbeta3 on the expression of K(Ca).
Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5513, USA.
Kwon-Seok
KS
Chae
Stuart E
SE
Dryer
D000199:Actins / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D019921:Biotinylation / Q000379:methods; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique / Q000379:methods; D005726:Ganglia, Parasympathetic / Q000166:cytology* / Q000196:embryology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000494:pharmacology; D015151:Immunoblotting / Q000379:methods; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal / Q000379:methods; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018408:Patch-Clamp Techniques / Q000379:methods; D010766:Phosphorylation; D010957:Plasmids / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014162:Transfection / Q000379:methods; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053782:Transforming Growth Factor beta3; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D000199:Actins; D004791:Enzyme Inhibitors; D006360:Heat-Shock Proteins; D024681:Potassium Channels, Calcium-Activated; D016212:Transforming Growth Factor beta; D053782:Transforming Growth Factor beta3; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium