title: Dysregulated expression of secretogranin III is involved in neurotoxin-induced dopaminergic neuron apoptosis.
abstract: The neurotoxins paraquat (PQ) and dopamine (DA or 6-OHDA) cause apoptosis of dopaminergic neurons in the substantia nigra pars compacta (SNpc), reproducing an important pathological feature of Parkinson's disease (PD). Secretogranin III (SCG3), a member of the multifunctional granin family, plays a key role in neurotransmitter storage and transport and in secretory granule biogenesis, which involves the uptake of exogenous toxins and endogenous "toxins" in neuroendocrine cells. However, the molecular mechanisms of neurotoxin-induced apoptosis in dopaminergic neurons and the role of SCG3-associated signaling pathways in neuroendocrine regulation are unclear. To address this, we used PQ- and DA-induced apoptosis in SH-SY5Y human dopaminergic cells as an in vitro model to investigate the association between SCG3 expression level and apoptosis. SCG3 was highly expressed in SH-SY5Y cells, and SCG3 mRNA and protein levels were dramatically decreased after PQ treatment. Apoptosis induced by PQ is associated with caspase activation and decreased SCG3 expression, and restoration of SCG3 expression is observed after treatment with caspase inhibitors. Overexpressed SCG3 in nonneuronal cells and endogenous SCG3 in SH-SY5Y cells are cleaved into specific fragments by recombinant caspase-3 and -7, but the fragments were not detected in PQ-treated SH-SY5Y cells. Therefore, SCG3 may be involved in apoptosis signal transduction as a caspase substrate, leading to loss of its original biological functions. In addition, SCG3 may be a pivotal component of the neuroendocrine pathway and play an important role in neuronal communication and neurotransmitter release, possibly representing a new potential target in the course of PD pathogenesis.
authors.affiliation: School of Forensic Medicine, China Medical University, Shenyang, Liaoning, People's Republic of China.
authors.forename: Fengrui
authors.initials: F
authors.lastname: Li
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Tian
authors.forename: Yishu
authors.initials: Y
authors.lastname: Zhou
authors.forename: Lanhui
authors.initials: L
authors.lastname: Zhu
authors.forename: Baojie
authors.initials: B
authors.lastname: Wang
authors.forename: Mei
authors.initials: M
authors.lastname: Ding
authors.forename: Hao
authors.initials: H
authors.lastname: Pang
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D061945:Caspase Inhibitors / Q000494:pharmacology; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D002864:Chromogranins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004298:Dopamine / Q000633:toxicity; D059290:Dopaminergic Neurons / Q000187:drug effects* / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D057809:HEK293 Cells / Q000378:metabolism; D006801:Humans; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009447:Neuroblastoma / Q000473:pathology; D009498:Neurotoxins / Q000633:toxicity*; D016627:Oxidopamine / Q000633:toxicity; D010269:Paraquat / Q000633:toxicity*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D013379:Substrate Specificity
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D002864:Chromogranins; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C506136:SCG3 protein, human; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D016627:Oxidopamine; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D010269:Paraquat; D004298:Dopamine