Downregulation of Platelet-Derived Growth Factor-α Receptor-Mediated Tyrosine Kinase Activity as a Cellular Mechanism for K⁺-Channel Regulation during Oligodendrocyte DevelopmentIn 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 2Ј,3Ј-cyclic nucleotide 3Ј-phosphodiesterase (CNP)-promoter driven enhanced green fluorescent protein expression and whole-cell capacitance measurements permitted a reliable distinction between subcortical white matter NG2 ϩ oligodendrocyte progenitors (OPs) and O4 ϩ preoligodendrocytes (pre-OLs) in situ. We focused on K ϩ 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 (I KDR ) between the NG2 ϩ and O4 ϩ stages but no significant changes in transient K ϩ -channel current (I KA ) amplitude. Tyrosine kinase inhibition in NG2 ϩ cells reduced I KDR amplitude with no effect on I KA , which mimicked the endogenous changes observed between OPs and pre-OLs. Tyrosine kinase inhibition also reduced the proliferative capacity of NG2 ϩ OPs in slice cultures. Conversely, acute platelet-derived growth factor receptor-␣ (PDGFR-␣) activation caused an increase of I KDR in NG2 ϩ but not in O4 ϩ cells. Consistent with this finding, PDGFR-␣ immunoreactivity was confined to NG2 ϩ cells with undetectable levels in O4 ϩ cells, suggesting that PDGFR-␣ signaling is absent in pre-OLs in situ. Importantly, the PDGF-induced increase of I KDR in NG2 ϩ cells was prevented by tyrosine kinase inhibition. Together, these data indicate that PDGFR-␣ and tyrosine kinase activity act via a common pathway that influences functional expression of K ϩ channels and proliferative capacity of OPs in situ.

Identification of Sox17 as a Transcription Factor That Regulates Oligodendrocyte Development

“…We demonstrated that, in the CNP-EGFP mouse, expression of O4 in white matter regions corresponds to a postmitotic stage of the oligodendrocyte lineage (Chittajallu et al, 2005). These findings are further supported by our analysis in cultured OPCs, demonstrating that (1) Sox17 protein levels increase during the morphological conversion of bipolar OPCs to multipolar preoligodendrocytes, and (2) Sox17 immunoreactivity is significantly higher in O4 ϩ preoligodendrocytes that in OPCs or oligodendrocytes.…”

Potassium Channel Subfamily K Member 3 (KCNK3) Contributes to the Development of Pulmonary Arterial Hypertension

“…For instance, endothelin-1, an extremely powerful vasoconstrictor that is involved in vascular remodeling, has been shown to inhibit KCNK3 via Rho kinase in human PASMCs. [41][42] Growth factor signaling, such as PDGF receptor and tyrosine kinase activity, act via a common pathway that influences the function and expression of K + channels [43][44] and could also partially explain the decrease in I KCNK3 . Moreover, downstream of the PDGF or tyrosine kinase receptors, Src kinase signaling is crucial for K + channel function, including TASK1/KCNK3.…”

NG2 cell response in the CNP‐EGFP mouse after contusive spinal cord injury

“…Prior to whole-cell recording of currents, series resistances values ranged between 4 to 12 MΩ and were compensated by at least 75%. Delayed rectifying (K DR ) and transient (K A ) potassium currents were isolated as previously described (Chittajallu et al, 2004; Chittajallu et al, 2005). Biocytin/NG2 and biocytin/O4 staining was performed as previously described (Chittajallu et al, 2005).…”