Activation of transcription factor Nrf-2 and its downstream targets in response to moloney murine leukemia virus ts1-induced thiol depletion and oxidative stress in astrocytes.
The neuroimmunodegenerative syndrome that develops in mice infected with ts1, a mutant of Moloney murine leukemia virus, resembles human AIDS. Both ts1 and human immunodeficiency virus type 1 infect astrocytes, microglia, and oligodendrocytes but do not infect neurons. Oxidative stress has been implicated in the neuropathology of AIDS dementia and other neurodegenerative diseases. We report here that ts1 infection of astrocytes (both transformed C1 cells and primary cultures) also induces thiol (i.e., glutathione and cysteine) depletion and reactive oxygen species (ROS) accumulation, events occurring in parallel with viral envelope precursor gPr80(env) accumulation and upregulated expression of endoplasmic reticulum chaperones GRP78 and GRP94. Furthermore, ts1-infected astrocytes mobilize their thiol redox defenses by upregulating levels of the Nrf-2 transcription factor, as well its targets, the xCT cystine/glutamate antiporter, gamma-glutamylcysteine ligase, and glutathione peroxidase. Depleting intracellular thiols by treating uninfected astrocytes with buthionine sulfoximine (BSO), a glutathione synthesis inhibitor, or by culturing in cystine-deficient medium, also induces ROS accumulation, activates Nrf-2, and upregulates Nrf-2 target gene expression in these astrocytes. Overexpression of Nrf-2 in astrocytes specifically increases expression of the above thiol synthesis-related proteins. Further treatment with BSO or N-acetylcysteine in transfected cells modulates this expression. Thiol depletion also accelerates cell death, while thiol supplementation promotes survival of ts1-infected cells. Together, our results indicate that ts1 infection of astrocytes, along with ts1-induced gPr80(env) accumulation, endoplasmic reticulum stress, thiol depletion, and oxidative stress, accelerates cell death; in response to the thiol depletion and oxidative stress, astrocytes activate their Nrf-2-mediated thiol antioxidant defenses, promoting cell survival.
Qiang
Wenan
W
University of Texas, M. D. Anderson Cancer Center, Science Park-Research Division, P.O. Box 389, Smithville, TX 78957, USA.
Cahill
Jodi M
JM
Liu
Jinrong
J
Kuang
Xianghong
X
Liu
Na
N
Scofield
Virginia L
VL
Voorhees
Jennifer R
JR
Reid
Amy J
AJ
Yan
Mingshan
M
Lynn
William S
WS
Wong
Paul K Y
PK
D027182:Amino Acid Transport System y+ / Q000502:physiology; D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000821:virology*; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D006861:Hydrogen Peroxide / Q000378:metabolism; D051379:Mice; D008979:Moloney murine leukemia virus / Q000502:physiology*; D051267:NF-E2-Related Factor 2; D018384:Oxidative Stress; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D015534:Trans-Activators / Q000502:physiology*; D014779:Virus Replication
D027182:Amino Acid Transport System y+; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; C492255:Slc7a11 protein, mouse; D013438:Sulfhydryl Compounds; D015534:Trans-Activators; D006861:Hydrogen Peroxide