Characterization of ABC transporter ABCB1 expressed in human neural stem/progenitor cells

Abstract

We investigated the localization and functional expression of the ABC transporter ABCB1 in human fetal neural stem/progenitor cells (hNSPCs). RT-PCR analysis revealed ABCB1 gene expression in hNSPCs. We found a single band in immunoblotted hNSPCs lysates probed with ABCB1 antibody, and detected ABCB1 at the hNSPCs cell membrane by immunocytochemistry and subcellular fractionation. ABCB1 inhibitors and substrate, and ATP-depleting agents enhanced hNSPCsÕ rhodamine 123 accumulation, and hNSPCs microsomes had vanadate-sensitive ATPase activity. ABCB1 and nestin expression decreased during hNSPCs differentiation, while the astroglial marker GFAP increased. ABCB1 may maintain hNSPCs in an undifferentiated state and could be a neural stem/progenitor marker.

ABC transporters, neural stem cells and neurogenesis – a different perspective

“…Further study revealed that cultured hNSPCs expressed functional ABCB1 as well as ABCG2 at the cell surface, and that their expression was downregulated during differentiation of hNSPCs, similar to the downregulation of ABCG2 in HSCs at the stage of lineage commitment [143,167,168]. It was observed that both ABC transporters were downregulated during hNSPC differentiation, together with nestin downregulation and GFAP upregulation (Figures 2 Cell Research | www.cell-research.com ABC transporters and neurogenesis 864 npg and 3).…”

“…It was found that more than half of the hNSPCs within neurospheres expressed nestin, an NSPC marker [167,168]. Furthermore, all nestin+ cells simultaneously expressed ABCB1 [167,168].…”

“…It was found that more than half of the hNSPCs within neurospheres expressed nestin, an NSPC marker [167,168]. Furthermore, all nestin+ cells simultaneously expressed ABCB1 [167,168]. Moreover, when the hNSPCs were isolated by fluorescence activated cell sorting (FACS) using the ABCB1 antibody, there was an increase in nestin+ cells compared to cells separated by control IgG (Islam et al, unpublished observation).…”

“…It was observed that both ABC transporters were downregulated during hNSPC differentiation, together with nestin downregulation and GFAP upregulation (Figures 2 Cell Research | www.cell-research.com ABC transporters and neurogenesis 864 npg and 3). The downregulation of nestin and upregulation of GFAP are considered to be indicators of stem/progenitor differentiation or maturation, and therefore it was proposed that ABCB1 and ABCG2 may be markers of neural stem/progenitor cells, and may have a functional role in upholding the undifferentiated status of hNSPCs [167,168]. Consistent with this idea, it was found that ABCG2 had a high substrate-stimulated ATP-hydrolysis activity in these cells, further suggesting that the ABCG2 transporter was functionally active in hNSPCs and may play a regulatory role in the maintenance of the undifferentiated state, possibly through modulating the uptake of small hydrophobic molecules involved in differentiation [147,155,168].…”

“…Interestingly, the correlation between nestin and ABCB1 expression in hNSPCs, and inhibition of hNSCPs proliferation by an ABCB1 (5) The hypothesis suggests that expression of the ABC transporters in NSCs may have an effect on NSC differentiation or proliferation, such that significant upregulation of ABCB1 or ABCG2 expression may lead to an increase in self-renewal of NSCs, and correspondingly, a decrease in ABCB1 or ABCG2 expression may lead to increased differentiation of NSCs. npg inhibitor (cyclosporine A) at a very low dose, suggested that the ABC transporter may contribute to neural stem/ progenitor cell expansion [167,168]. While ABCA2 shows higher expression in nestin+ mouse neural progenitors, at later developmental stages it undergoes a conspicuous downregulation, persisting only in limited subsets of differentiated neurons [166].…”