title: Sciatic nerve conditioned medium depleted of pro-NGF modulates sodium currents and neurite outgrowth in PC12 cells.
abstract: Excitability and axon/dendrite specification are the most distinctive features in the establishment of neuronal polarization. Conditioned medium from rat sciatic nerve (CM) induced a neuronal-like morphology in PC12 cells. Here we show that CM neuritogenic activity is limited to the induction of dendrites in PC12 cells. However, treatment of these cells with CM in combination with a generic inhibitor for tyrosine kinase receptors (k252a) promoted the enhancement of neurite length, development of axons and induction of sodium currents. On the other hand, specific inhibition of TrkA and p75(NTR) receptors in CM-treated cells reduced the neurite length in comparison with cells treated only with CM, although the effect over the induction of sodium currents was continuously observed. These results suggested that CM had some components that, even though are able to start the morphological cell differentiation and produce short neurites (likely acting through TrkA and p75(NTR)), can restrain further neurite extension. Depletion of pro-NGF isoforms from CM produced a similar effect as the exerted by k252a, TrkA and p75(NTR) receptor inhibitors in CM-treated cells, inducing the elicitation of sodium currents. These results suggested that the effect of CM might be mediated through pro-NGF. The difference between the results obtained with the generic inhibitor for Trk receptors and the specific inhibitors for TrkA and p75(NTR) receptors in CM-treated cells, suggested that alternative pathways could be used to regulate neurite elongation, axon specification and sodium currents in PC12 cells. These findings represent important clues to improve the understanding of the initiation of neuronal polarity.
authors.affiliation: Unidad de Neurociencias, Centro de Biociencias y Medicina Molecular, Instituto de Estudios Avanzados, Apartado 17606, Caracas 1015 A, Venezuela. mlongart@idea.gob.ve
authors.forename: M
authors.initials: M
authors.lastname: Longart
authors.forename: L
authors.initials: L
authors.lastname: García
authors.forename: C
authors.initials: C
authors.lastname: Castillo
authors.forename: J C
authors.initials: JC
authors.lastname: Martínez
authors.forename: R
authors.initials: R
authors.lastname: Medina
authors.forename: P
authors.initials: P
authors.lastname: Forsyth
authors.forename: C
authors.initials: C
authors.lastname: Malavé
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002227:Carbazoles / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D047468:Immunoprecipitation / Q000379:methods; D026121:Indole Alkaloids / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology; D009414:Nerve Growth Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016501:Neurites / Q000187:drug effects / Q000502:physiology*; D016900:Neurofilament Proteins / Q000378:metabolism; D016716:PC12 Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D011498:Protein Precursors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor / Q000037:antagonists & inhibitors; D020917:Receptor, trkA / Q000037:antagonists & inhibitors; D012584:Sciatic Nerve / Q000737:chemistry*; D015222:Sodium Channels / Q000378:metabolism*; D013997:Time Factors; D046509:Tissue Culture Techniques
chemical_list: D002227:Carbazoles; D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors; D026121:Indole Alkaloids; C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D009414:Nerve Growth Factors; D016900:Neurofilament Proteins; D011498:Protein Precursors; D020800:Receptor, Nerve Growth Factor; D015222:Sodium Channels; C514218:pro-nerve growth factor, rat; C051774:neurofilament protein H; D020932:Nerve Growth Factor; C049985:staurosporine aglycone; D020917:Receptor, trkA