title: Neural agrin changes the electrical properties of developing human skeletal muscle cells.
abstract: Recent investigations suggest that the effects of neural agrin might not be limited to neuromuscular junction formation and maintenance and that other aspects of muscle development might be promoted by agrin. Here we tested the hypothesis that agrin induces a change in the excitability properties in primary cultures of non-innervated human myotubes. Electrical membrane properties of human myotubes were recorded using the whole-cell patch-clamp technique. Cell incubation with recombinant chick neural agrin (1 nM) led to a more negative membrane resting potential. Addition of strophanthidin, a blocker of the Na(+)/K(+) ATPase, depolarized agrin-treated myotubes stronger than control, indicating, in the presence of agrin, a higher contribution of the Na(+)/K(+) ATPase in establishing the resting membrane potential. Indeed, larger amounts of both the alpha1 and the alpha2 isoforms of the Na(+)/K(+) ATPase protein were expressed in agrin-treated cells. A slight but significant down-regulation of functional apamin-sensitive K(+) channels was observed after agrin treatment. These results indicate that neural agrin might act as a trophic factor promoting the maturation of membrane electrical properties during differentiation, confirming the role of agrin as a general promoter of muscle development.
authors.affiliation: Department of Physiology and Pathology, BRAIN Centre for Neuroscience, University of Trieste, Trieste, Italy.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Jurdana
authors.forename: Guido
authors.initials: G
authors.lastname: Fumagalli
authors.forename: Zoran
authors.initials: Z
authors.lastname: Grubic
authors.forename: Paola
authors.initials: P
authors.lastname: Lorenzon
authors.forename: Tomaz
authors.initials: T
authors.lastname: Mars
authors.forename: Marina
authors.initials: M
authors.lastname: Sciancalepore
mesh_terms: D000293:Adolescent; D018171:Agrin / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D002645:Chickens; D002648:Child; D002675:Child, Preschool; D055724:Electrophysiological Phenomena / Q000187:drug effects*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008856:Microscopy, Fluorescence; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D018171:Agrin; D021122:Protein Subunits; D051640:Small-Conductance Calcium-Activated Potassium Channels; D000254:Sodium-Potassium-Exchanging ATPase