The neuro-steroid, 5-androstene 3β,17α diol; induces endoplasmic reticulum stress and autophagy through PERK/eIF2α signaling in malignant glioma cells and transformed fibroblasts.
In this study, we identified a mechanism by which the neuro-steroid, 5-androstene 3β,17α diol (17α-AED) induces autophagy in human malignant glioma cells and transformed fibroblasts. 17α-AED treatment induced endoplasmic reticulum (ER) stress, identified by the partial activation of an unfolded protein response in T98G, U87MG, U251MG, LN-18, LN-229 and LN-Z308 glioma cell lines. In this regard, there were increased levels of CCAAT/enhancer-binding protein homologous protein (CHOP) and glucose-regulated protein of 78kDa transcripts but no splicing of X-box-binding protein 1 mRNA or processing of activating transcription factor-6 in glioma cells treated with the neuro-steroid. 17α-AED induced eukaryotic translational initiation factor 2α (eIF2α) phosphorylation in glioma cells which correlated with microtubule-associated protein-light chain 3 (LC3) conversion from LC3-I to -II. In transformed murine embryonic fibroblasts (MEFs) that are deficient of eIF2α function or T98G glioma cells transfected with a dominant-negative eIF2α construct, 17α-AED induced LC3 conversion was significantly reduced as compared to control cells. Neuro-steroid treatment caused the activation of the eIF2α kinase, protein kinase-like ER kinase (PERK) but not other eIF2α kinases in glioma cells. Moreover, eIF2α phosphorylation and LC3 conversion, in response to 17α-AED treatment, was blocked in MEFs that lacked PERK activity. T98G cells transfected with a dominant-negative PERK construct exhibited an attenuated response to neuro-steroid treatment in terms of decreases in: eIF2α activation; CHOP expression; the incidence of autophagy; and cytotoxicity. These results demonstrate that ER stress is linked to 17α-AED induced autophagy by PERK/eIF2α signaling in human malignant glioma cells and transformed fibroblasts.
Jia
Wentao
W
Department of Neurosurgery, Virginia Commonwealth University, P.O. Box 980631, Richmond, VA 23298-0631, USA.
Loria
Roger M
RM
Park
Margaret A
MA
Yacoub
Adly
A
Dent
Paul
P
Graf
Martin R
MR
D000734:Androstenediols / Q000494:pharmacology*; D000818:Animals; D001343:Autophagy / Q000502:physiology; D002461:Cell Line, Transformed; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005910:Glioma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008819:Mice, Nude; D010766:Phosphorylation; D015398:Signal Transduction; D014162:Transfection; D019892:eIF-2 Kinase / Q000378:metabolism*
D000734:Androstenediols; D019892:eIF-2 Kinase