title: 1-Benzyl-1,2,3,4-tetrahydroisoquinoline binds with tubulin beta, a substrate of parkin, and reduces its polyubiquitination.
abstract: Substances that mimic the actions of causative gene products of familial Parkinson's disease (PD) are candidate as causative agents of idiopathic PD. 1-Benzyl-1,2,3,4-tetrahydroisoquinoline (1BnTIQ), an endogenous neurotoxin, is present at three times higher levels in CSF of PD patients than in CSF of control subjects. However, the mechanism of 1BnTIQ's neurotoxicity is unclear. In this study, we tried to identify 1BnTIQ-binding proteins by using a diazido-functionalized 1BnTIQ analog, 1-(3-azido-5-azidomethylbenzyl)-1,2,3,4-tetrahydroisoquinoline, designed and synthesized as a probe for radioisotope-free photoaffinity labeling. One major photolabeled protein identified using this probe was tubulin beta, which has been reported to be a substrate of parkin, a ubiquitin E3 ligase and a causative gene product of familial PD. Loss of function mutation of parkin is reported to result in loss of tubulin beta ubiquitination. Therefore, we examined the effect of 1BnTIQ on ubiquitination of tubulin beta. The polyubiquitinated tubulin beta level in human neuroblastoma SH-SY5Y cells was reduced in the presence of 1BnTIQ, even at concentrations as low as those detected in parkinsonian CSF. In vitro ubiquitination assay gave similar results. It is suggested that 1BnTIQ has the same effect on tubulin ubiquitination as does mutant parkin in familial PD. Taken together, substances which reduce polyubiquitination of tubulin such as 1BnTIQ are supposed to be candidates of etiological factors of PD.
authors.affiliation: Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Ryuki
authors.initials: R
authors.lastname: Kohta
authors.forename: Yaichiro
authors.initials: Y
authors.lastname: Kotake
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Hosoya
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Hiramatsu
authors.forename: Yuko
authors.initials: Y
authors.lastname: Otsubo
authors.forename: Hiroko
authors.initials: H
authors.lastname: Koyama
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hirokane
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Yokoyama
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Ikeshoji
authors.forename: Ken
authors.initials: K
authors.lastname: Oofusa
authors.forename: Masaaki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Ohta
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000502:physiology*; D006801:Humans; D051379:Mice; D009498:Neurotoxins / Q000378:metabolism* / Q000633:toxicity; D010300:Parkinson Disease / Q000209:etiology / Q000378:metabolism; D025821:Polyubiquitin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D013379:Substrate Specificity / Q000502:physiology; D044005:Tetrahydroisoquinolines / Q000378:metabolism* / Q000633:toxicity; D014404:Tubulin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination / Q000502:physiology
chemical_list: D009498:Neurotoxins; D044005:Tetrahydroisoquinolines; D014404:Tubulin; D025821:Polyubiquitin; D044767:Ubiquitin-Protein Ligases; C111567:parkin protein; C084924:1,2,3,4-tetrahydro-1-(phenylmethyl)isoquinoline