title: Downregulation of platelet-derived growth factor-alpha receptor-mediated tyrosine kinase activity as a cellular mechanism for K+-channel regulation during oligodendrocyte development in situ.
abstract: Oligodendrocyte maturation has been defined based on expression of developmentally regulated antigens. However, transitions at early stages of the lineage have not been functionally characterized fully in situ. Combining 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP)-promoter driven enhanced green fluorescent protein expression and whole-cell capacitance measurements permitted a reliable distinction between subcortical white matter NG2+ oligodendrocyte progenitors (OPs) and O4+ preoligodendrocytes (pre-OLs) in situ. We focused on K+ channels because their expression has been associated previously with the proliferation and differentiation potential of OPs. Using whole-cell patch clamp, we observed a downregulation of the delayed outward-rectifying current (IKDR) between the NG2+ and O4+ stages but no significant changes in transient K+-channel current (IKA) amplitude. Tyrosine kinase inhibition in NG2+ cells reduced IKDR amplitude with no effect on IKA, which mimicked the endogenous changes observed between OPs and pre-OLs. Tyrosine kinase inhibition also reduced the proliferative capacity of NG2+ OPs in slice cultures. Conversely, acute platelet-derived growth factor receptor-alpha (PDGFR-alpha) activation caused an increase of IKDR in NG2+ but not in O4+ cells. Consistent with this finding, PDGFR-alpha immunoreactivity was confined to NG2+ cells with undetectable levels in O4+ cells, suggesting that PDGFR-alpha signaling is absent in pre-OLs in situ. Importantly, the PDGF-induced increase of IKDR in NG2+ cells was prevented by tyrosine kinase inhibition. Together, these data indicate that PDGFR-alpha and tyrosine kinase activity act via a common pathway that influences functional expression of K+ channels and proliferative capacity of OPs in situ.
authors.affiliation: Center for Neuroscience Research, Children's Research Institute, Children's National Medical Center, Washington, DC 20010, USA. rchittajallu@cnmcresearch.org
authors.forename: Ramesh
authors.initials: R
authors.lastname: Chittajallu
authors.forename: Adan A
authors.initials: AA
authors.lastname: Aguirre
authors.forename: Vittorio
authors.initials: V
authors.lastname: Gallo
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009836:Oligodendroglia / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000037:antagonists & inhibitors* / Q000502:physiology*
chemical_list: D015221:Potassium Channels; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases; D020796:Receptor, Platelet-Derived Growth Factor alpha