title: Expression and localisation of brain-type organic cation transporter (BOCT/24p3R/LCN2R) in the normal rat hippocampus and after kainate-induced excitotoxicity.
abstract: The iron siderophore binding protein lipocalin 2 (LCN2, also known as 24p3, NGAL and siderocalin) may be involved in iron homeostasis, but to date, little is known about expression of its putative receptor, brain-type organic cation transporter (BOCT, also known as BOCT1, 24p3R, NGALR and LCN2R), in the brain during neurodegeneration. The present study was carried out to elucidate the expression of LCN2 and BOCT in hippocampus after excitotoxicity induced by the glutamate analog, kainate (KA) and a possible role of LCN2 in neuronal injury. As reported previously, a rapid and sustained induction in expression of LCN2 was found in the hippocampus after intracerebroventicular injection of KA. BOCT was expressed in neurons of the saline-injected control hippocampus, and immunolabel for BOCT protein was preserved in pyramidal neurons of CA1 at 1 day post-KA injection, likely due to the delayed onset of neurodegeneration after KA injection. At 3 days and 2 weeks after KA injections, loss of immunolabel was observed due to degenerated neurons, although remaining neurons continued to express BOCT, and induction of BOCT was found in OX-42 positive microglia. This resulted in an overall decrease in BOCT mRNA and protein expression after KA treatment. Increased expression of the pro-apoptotic marker, Bim, was found in both neurons and microglia after KA injection, but TUNEL staining indicating apoptosis was found primarily in Bim-expressing neurons, but not microglia. Interaction between LCN2 and BOCT was found by DuoLink assay in cultured hippocampal neurons. Apo-LCN2 without iron caused no significant differences in neuronal Bim expression or cell survival, whereas holo-LCN2 consisting of LCN2:iron:enterochelin complex increased Bim mRNA expression and decreased neuronal survival. Together, results suggest that LCN2 and BOCT may have a role in neuronal injury.
authors.affiliation: Department of Pharmacology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, Singapore 117597; National University of Singapore Graduate School for Integrative Sciences and Engineering, Centre for Life Sciences, National University of Singapore, 28 Medical Drive, Singapore 117456; Neurobiology and Ageing Programme, Life Sciences Institute, Centre for Life Sciences, National University of Singapore, 28 Medical Drive, Singapore 117456.
authors.forename: Wan-Jie
authors.initials: WJ
authors.lastname: Chia
authors.affiliation: Department of Pharmacology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, Singapore 117597; Neurobiology and Ageing Programme, Life Sciences Institute, Centre for Life Sciences, National University of Singapore, 28 Medical Drive, Singapore 117456; Singapore Institute for Neurotechnology (SINAPSE), Centre for Life Sciences, 28 Medical Drive, Singapore 117456.
authors.forename: Francis Chee Kuan
authors.initials: FC
authors.lastname: Tan
authors.affiliation: Neurobiology and Ageing Programme, Life Sciences Institute, Centre for Life Sciences, National University of Singapore, 28 Medical Drive, Singapore 117456; Department of Anatomy, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 4 Medical Drive, Singapore 117597. Electronic address: wei_yi_ong@nuhs.edu.sg.
authors.forename: Wei-Yi
authors.initials: WY
authors.lastname: Ong
authors.affiliation: Department of Pharmacology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, 10 Medical Drive, Singapore 117597; National University of Singapore Graduate School for Integrative Sciences and Engineering, Centre for Life Sciences, National University of Singapore, 28 Medical Drive, Singapore 117456; Neurobiology and Ageing Programme, Life Sciences Institute, Centre for Life Sciences, National University of Singapore, 28 Medical Drive, Singapore 117456; Singapore Institute for Neurotechnology (SINAPSE), Centre for Life Sciences, 28 Medical Drive, Singapore 117456. Electronic address: gavindawe@nus.edu.sg.
authors.forename: Gavin S
authors.initials: GS
authors.lastname: Dawe
mesh_terms: D000818:Animals; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D007608:Kainic Acid / Q000494:pharmacology*; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar
chemical_list: D018690:Excitatory Amino Acid Agonists; D027701:Organic Cation Transport Proteins; D012333:RNA, Messenger; D007608:Kainic Acid
keywords: Apoptosis; BOCT; Bim; Iron; Lipocalin 2; Lipocalins; Megalin; Neurodegeneration; Siderophore