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6-Hydroxydopamine induces secretion of PARK7/DJ-1 via autophagy-based unconventional secretory pathway.

ABSTRACT: PARK7/DJ-1 is a Parkinson disease- and cancer-associated protein that functions as a multifunctional protein involved in gene transcription regulation and anti-oxidative defense. Although PARK7 lacks the secretory signal sequence, it is secreted and plays important physiological and pathophysiological roles. Whereas secretory proteins that lack the endoplasmic reticulum-targeting signal sequence are secreted from cells by way of what is called the unconventional secretion mechanism, the specific processes responsible for causing PARK7 to be secreted across the plasma membrane have remained unclear. In the present study, we found that PARK7 secretion was increased by treatment with 6-OHDA via the unconventional secretory pathway in human neuroblastoma SH-SY5Y cells and MEF cells. We also found that 6-OHDA-induced PARK7 secretion was suppressed in Atg5-, Atg9-, or Atg16l1-deficient MEF cells or ATG16L1 knockdown SH-SY5Y cells, indicating that the autophagy-based unconventional secretory pathway is involved in PARK7 secretion. We moreover observed that 6-OHDA-derived electrophilic quinone induced oxidative stress as indicated by a decrease in glutathione levels, and that this was suppressed by pretreatment with antioxidant NAC. We further found that NAC treatment suppressed autophagy and PARK7 secretion. We also observed that 6-OHDA-induced autophagy was associated with activation of AMPK and ULK1 via a pathway which was independent of MTOR. Collectively these results suggest that electrophilic 6-OHDA quinone enhances oxidative stress, and that this is followed by AMPK-ULK1 pathway activation and induction of secretory autophagy to produce unconventional secretion of PARK7. ABBREVIATIONS:6-OHDA: 6-hydroxydopamine; AMPK: AMP-activated protein kinase; ATG: autophagy related; CAV1: caveolin 1; ER: endoplasmic reticulum; FN1: fibronectin 1; GSH: glutathione; IDE: insulin degrading enzyme; IL: interleukin; LDH: lactate dehydrogenase; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MEF: mouse embryonic fibroblast; MTOR: mechanistic target of rapamycin kinase; NAC: N-acetyl-L-cysteine; PARK7/DJ-1: Parkinsonism associated deglycase; PD: Parkinson disease; RPS6KB1/p70S6K: ribosomal protein S6 kinase B1; RPN1: ribophorin I; ROS: reactive oxygen species; ULK1: unc-51 like autophagy activating kinase 1; WT: wild-type.

SUBMITTER: Urano Y

PROVIDER: S-EPMC6152502 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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6-Hydroxydopamine induces secretion of PARK7/DJ-1 via autophagy-based unconventional secretory pathway.

Urano Yasuomi Y Mori Chinatsu C Fuji Ayano A Konno Keito K Yamamoto Takayuki T Yashirogi Shohei S Ando Mayu M Saito Yoshiro Y Noguchi Noriko N

Autophagy 20180816 11

PARK7/DJ-1 is a Parkinson disease- and cancer-associated protein that functions as a multifunctional protein involved in gene transcription regulation and anti-oxidative defense. Although PARK7 lacks the secretory signal sequence, it is secreted and plays important physiological and pathophysiological roles. Whereas secretory proteins that lack the endoplasmic reticulum-targeting signal sequence are secreted from cells by way of what is called the unconventional secretion mechanism, the specific ...[more]

PMID: 30112966

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Project description:Appropriate glucagon secretion from pancreatic alpha cells in response to hypoglycemia is an important component of maintaining glucose homeostasis. Dysregulated glucagon secretion leads to the delayed recovery from a hypoglycemic attack in type 1 diabetes patients which can be lethal. Although elucidating the precise mechanism of glucagon secretion in hypoglycemia is warranted, the underlying mechanism remains poorly understood.The present study provides evidence of the role of autophagy in glucagon secretion in hypoglycemia by demonstrating that autophagy regulates adrenergic stimulation of glucagon secretion downstream of beta2 adrenergic receptor. First, from the analyses of T1D human islets and the published database of scRNA-seq of T1D human alpha cells, we described autophagy pathways altered in T1D alpha cells. Second, we generated alpha cell-specific Atg7KO mice (alphaAtg7KO) and clarified that the lack of autophagy in alpha cells impairs the reactive glucagon secretion in acute hypoglycemia. Third, to interrogate the molecular mechanism of autophagy-mediated glucagon regulation, we analyzed top genes downregulated inT1D and T2D alpha cells and found the expression of beta2 adrenergic receptor showed significant down-regulation in T1D alpha cells. We confirmed the decreased expression of beta2 adrenergic receptor in alpha cells of the T1D pancreas section, the islets of alphaAtg7KO mice, and a murine alpha cell line with stable knockdown of Atg7. Furthermore, in vivo and ex vivo studies of alphaAtg7KO mice exhibited that lack of autophagy led to the loss of stimulatory effect of beta2-adrenergic signaling on glucagon secretion. Finally, we established the Atg7 knockdown model in sorted human alpha cells and confirmed the effect of autophagy on the expression of the beta2 adrenergic receptor. Together, our study provides novel insights into the regulatory role of autophagy in glucagon secretion in response to hypoglycemia and provides therapeutic options to achieve stable glycemic control in T1D patients.

Dataset Information

6-Hydroxydopamine induces secretion of PARK7/DJ-1 via autophagy-based unconventional secretory pathway.

Publications

6-Hydroxydopamine induces secretion of PARK7/DJ-1 via autophagy-based unconventional secretory pathway.

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