Ethanol-induced transcriptional activation of programmed cell death 4 (Pdcd4) is mediated by GSK-3β signaling in rat cortical neuroblasts.
Ingestion of ethanol (ETOH) during pregnancy induces grave abnormalities in developing fetal brain. We have previously reported that ETOH induces programmed cell death 4 (PDCD4), a critical regulator of cell growth, in cultured fetal cerebral cortical neurons (PCNs) and in the cerebral cortex in vivo and affect protein synthesis as observed in Fetal Alcohol Spectrum Disorder (FASD). However, the mechanism which activates PDCD4 in neuronal systems is unclear and understanding this regulation may provide a counteractive strategy to correct the protein synthesis associated developmental changes seen in FASD. The present study investigates the molecular mechanism by which ethanol regulates PDCD4 in cortical neuroblasts, the immediate precursor of neurons. ETOH treatment significantly increased PDCD4 protein and transcript expression in spontaneously immortalized rat brain neuroblasts. Since PDCD4 is regulated at both the post-translational and post-transcriptional level, we assessed ETOH's effect on PDCD4 protein and mRNA stability. Chase experiments demonstrated that ETOH does not significantly impact either PDCD4 protein or mRNA stabilization. PDCD4 promoter-reporter assays confirmed that PDCD4 is transcriptionally regulated by ETOH in neuroblasts. Given a critical role of glycogen synthase kinase 3β (GSK-3β) signaling in regulating protein synthesis and neurotoxic mechanisms, we investigated the involvement of GSK-3β and showed that multifunctional GSK-3β was significantly activated in response to ETOH in neuroblasts. In addition, we found that ETOH-induced activation of PDCD4 was inhibited by pharmacologic blockade of GSK-3β using inhibitors, lithium chloride (LiCl) and SB-216763 or siRNA mediated silencing of GSK-3β. These results suggest that ethanol transcriptionally upregulates PDCD4 by enhancing GSK-3β signaling in cortical neuroblasts. Further, we demonstrate that canonical Wnt-3a/GSK-3β signaling is involved in regulating PDCD4 protein expression. Altogether, we provide evidence that GSK-3β/PDCD4 network may represent a critical modulatory point to manage the protein synthetic anomalies and growth aberrations of neural cells seen in FASD.
Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America.
Amanjot Kaur
AK
Riar
Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America; South Plains Alcohol and Addiction Research Center, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America.
Madhusudhanan
M
Narasimhan
Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America.
Mary Latha
ML
Rathinam
Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America.
Dhanashree
D
Vedpathak
Center for Personalized Medicine, South Texas Veterans Health Care System, and University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
Srinivas
S
Mummidi
Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America; South Plains Alcohol and Addiction Research Center, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America.
George I
GI
Henderson
Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America; South Plains Alcohol and Addiction Research Center, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America.
Lenin
L
Mahimainathan
D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D000431:Ethanol / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D058953:Neural Stem Cells / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D015533:Transcriptional Activation
D051017:Apoptosis Regulatory Proteins; C467042:Pdcd4 protein, rat; D000431:Ethanol; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3