Oxidative stress impairs autophagic flux in prion protein-deficient hippocampal cells

Oh, Jae Min; Choi, Eun Kyoung; Carp, Richard I.; Kim, Yong Sun

doi:10.4161/auto.21164

Cited by 42 publications

(45 citation statements)

References 63 publications

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“…These data comply with the findings of other groups demonstrating that autophagy is upregulated in PRNP-deficient cells. 53,54 Moreover, our findings are consistent with a connection between the endocytic pathway, autophagy, and exosome biogenesis and secretion. 33,34 It is well known that autophagosome maturation requires ESCRT function, and that autophagosomes are able to fuse with endocytic vesicles (as MVBs) or lysosomes, which contain the hydrolytic enzymes required to degrade autophagosomal content.…”

Section: Discussionsupporting

confidence: 88%

PRNP/prion protein regulates the secretion of exosomes modulating CAV1/caveolin-1-suppressed autophagy

et al. 2016

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Prion protein modulates many cellular functions including the secretion of trophic factors by astrocytes. Some of these factors are found in exosomes, which are formed within multivesicular bodies (MVBs) and secreted into the extracellular space to modulate cell-cell communication. The mechanisms underlying exosome biogenesis were not completely deciphered. Here, we demonstrate that primary cultures of astrocytes and fibroblasts from prnp-null mice secreted lower levels of exosomes than wild-type cells. Furthermore, prnp-null astrocytes exhibited reduced MVB formation and increased autophagosome formation. The reconstitution of PRNP expression at the cell membrane restored exosome secretion in PRNP-deficient astrocytes, whereas macroautophagy/autophagy inhibition via BECN1 depletion reestablished exosome release in these cells. Moreover, the PRNP octapeptide repeat domain was necessary to promote exosome secretion and to impair the formation of the CAV1-dependent ATG12-ATG5 cytoplasmic complex that drives autophagosome formation. Accordingly, higher levels of CAV1 were found in lipid raft domains instead of in the cytoplasm in prnp-null cells. Collectively, these findings demonstrate that PRNP supports CAV1-suppressed autophagy to protect MVBs from sequestration into phagophores, thus facilitating exosome secretion.

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Section: Discussionsupporting

confidence: 88%

PRNP/prion protein regulates the secretion of exosomes modulating CAV1/caveolin-1-suppressed autophagy

et al. 2016

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“…Perhaps related to SIRT1 inhibition, excess concentrations of glucose and palmitate may also impair autophagy through the generation of oxidative stress (4,8,15,40,72). Reactive oxygen species inhibit the activity of Atg4 (78), an enzyme required both for the maturation of LC3 prior to its incorporation into the forming autophagosomal membrane and for LC3 cleavage from the outside of the autolysosome to be recycled for future use (46).…”

Section: Discussionmentioning

confidence: 99%

Glucose and palmitate uncouple AMPK from autophagy in human aortic endothelial cells

Weikel

Cacicedo

Ruderman

et al. 2015

American Journal of Physiology-Cell Physiology

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Weikel KA, Cacicedo JM, Ruderman NB, Ido Y. Glucose and palmitate uncouple AMPK from autophagy in human aortic endothelial cells. Am J Physiol Cell Physiol 308: C249 -C263, 2015. First published October 29, 2014 doi:10.1152/ajpcell.00265.2014.-Dysregulated autophagy and decreased AMP-activated protein kinase (AMPK) activity are each associated with atherogenesis. Atherogenesis is preceded by high circulating concentrations of glucose and fatty acids, yet the mechanism by which these nutrients regulate autophagy in human aortic endothelial cells (HAECs) is not known. Furthermore, whereas AMPK is recognized as an activator of autophagy in cells with few nutrients, its effects on autophagy in nutrient-rich HAECs has not been investigated. We maintained and passaged primary HAECs in media containing 25 mM glucose and incubated them subsequently with 0.4 mM palmitate. These conditions impaired basal autophagy and rendered HAECs more susceptible to apoptosis and adhesion of monocytes, outcomes attenuated by the autophagy activator rapamycin. Glucose and palmitate diminished AMPK activity and phosphorylation of the uncoordinated-51-like kinase 1 (ULK1) at Ser555, an autophagy-activating site targeted by AMPK. 5-Aminoimidazole-4-carboxamide-1-␤-D-ribofuranoside (AICAR)-mediated activation of AMPK phosphorylated acetyl-CoA carboxylase, but treatment with AICAR or other AMPK activators (A769662, phenformin) did not restore ULK1 phosphorylation or autophagosome formation. To determine whether palmitate-induced ceramide accumulation contributed to this finding, we overexpressed a ceramidemetabolizing enzyme, acid ceramidase. The increase in acid ceramidase expression ameliorated the effects of excess nutrients on ULK1 phosphorylation, without altering the effects of the AMPK activators. Thus, unlike low nutrient conditions, AMPK becomes uncoupled from autophagy in HAECs in a nutrient-rich environment, such as that found in patients with increased cardiovascular risk. These findings suggest that combinations of AMPK-independent and AMPK-dependent therapies may be more effective alternatives than either therapy alone for treating nutrient-induced cellular dysfunction. endothelium; autophagy; palmitate; glucose; AMPK PATIENTS WITH THE METABOLIC SYNDROME or type 2 diabetes are more likely to develop cardiovascular complications such as atherosclerosis (26,44,54,62,77). Many cellular processes have been implicated in driving this pathology, but the predominant mechanisms remain unclear. Intriguing reports from humans and murine models of vascular disease indicate that dysregulation of macroautophagy, a pathway by which cellular components are recycled for energy utilization, may play a prominent role in this disease progression. Thus it has been shown that impairment of macroautophagy contributes to arterial aging (56), cardiomyocyte apoptosis (34), and aortic lesion formation (74).Macroautophagy (hereinafter referred to as "autophagy") is a process by which cellular components are engulfed in a double-membraned vesicle, the au...

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“…Western blotting was performed as described previously [27,28]. Briefly, cells were lysed in lysis buffer with protease inhibitors cocktail and phosphatase inhibitor cocktail.…”

Section: Methodsmentioning

confidence: 99%

Fibroblast Growth Factor 21 Protects Against High Glucose Induced Cellular Damage and Dysfunction of Endothelial Nitric-Oxide Synthase in Endothelial Cells

Wang

Song

Xiao

et al. 2014

Cell Physiol Biochem

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Aims: Fibroblast growth factor 21 (FGF21) is a powerful endocrine hormone modulating glucose and lipid metabolism and represents a promising drug for type 2 diabetes. The present study was to determine the effect of FGF21 on high glucose-induced damage and dysfunction in endothelial cells. Methods: The protein expression of β-klotho was examined in human umbilical vein endothelial cell (HUVECs) using immunofluorescence and Western blotting. HUVECs were cultured in medium with normal glucose (NG), high glucose (HG) and HG + FGF21 (30 nM). Cell viability, migration, reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase, nitric oxide (NO) production, intracellular cyclic guanosine monophosphate (cGMP) and endothelial nitric oxide synthase (eNOS) phosphorylation at Ser-1177/Ser-633 sites were measured. Results: β-klotho, the anchor protein of FGF21, is expressed in HUVECs. Administration of FGF21 prevented HG-induced impairment of cell viability, migration, oxidant stress, NO production and intracellular cGMP levels in HUVECs. FGF21 also rescued HG-induced decrease of eNOS phosphorylation at Ser-1177 and Ser-633. HG and FGF21 had no effects on eNOS phosphorylation at Ser-617 and Thr-495. Inhibition of AMP-activated protein kinase (AMPK), but not Akt or Ca²⁺/calmodulin-dependent protein kinase II, abolished the protective effect of FGF21 on eNOS phosphorylation at Ser-1177. The protective effect of FGF21 on eNOS phosphorylation at Ser-633 was also abolished by inhibition of AMPK but not by Akt or cAMP-dependent protein kinase A. Conclusion: Our results provide the first evidence that FGF21 protects against high glucose induced cell damage and eNOS dysfunction in an AMPK-dependent manner in HUVECs, and suggest that FGF21 may be a promoting therapeutic agent for vascular complications in diabetes.

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Oxidative stress impairs autophagic flux in prion protein-deficient hippocampal cells

Cited by 42 publications

References 63 publications

PRNP/prion protein regulates the secretion of exosomes modulating CAV1/caveolin-1-suppressed autophagy

PRNP/prion protein regulates the secretion of exosomes modulating CAV1/caveolin-1-suppressed autophagy

Glucose and palmitate uncouple AMPK from autophagy in human aortic endothelial cells

Fibroblast Growth Factor 21 Protects Against High Glucose Induced Cellular Damage and Dysfunction of Endothelial Nitric-Oxide Synthase in Endothelial Cells

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