Ethanol Exposure Transiently Elevates but Persistently Inhibits Tyrosine Kinase Activity and Impairs the Growth of the Nascent Apical Dendrite
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Dendritogenesis can be impaired by exposure to alcohol, and aspects of this impairment share phenotypic similarities to dendritic defects observed after blockade of the Reelin-Dab1 tyrosine kinase signaling pathway. In this study, we find that 10 min of alcohol exposure (400 mg/dL ethanol) by itself causes an unexpected increase in tyrosine phosphorylation of many proteins including Src and Dab1 that are essential downstream effectors of Reelin signaling. This increase in phosphotyrosine is dose-dependent and blockable by selective inhibitors of Src Family Kinases (SFKs). However, the response is transient, and phosphotyrosine levels return to baseline after 30 min of continuous ethanol exposure, both in vitro and in vivo. During this latter period, Src is inactivated and Reelin application cannot stimulate Dab1 phosphorylation. This suggests that ethanol initially activates but then silences the Reelin-Dab1 signaling pathway by brief activation and then sustained inactivation of SFKs. Time-lapse analyses of dendritic growth dynamics show an overall decrease in growth and branching compared to controls after ethanol-exposure that is similar to that observed with Reelin-deficiency. However, unlike Reelin-signaling disruptions, the dendritic filopodial speeds are decreased after ethanol exposure, and this decrease is associated with sustained dephosphorylation and activation of cofilin, an F-actin severing protein. These findings suggest that persistent Src inactivation coupled to cofilin activation may contribute to the dendritic disruptions observed with fetal alcohol exposure.
KeywordsFetal alcohol syndrome disorder Cortical development Src kinases Dab1 Dendritogenesis Cofilin
fetal alcohol spectrum disorder
Src family kinases
We thank members of the Olson lab and Krysten O’Hara for assistance and valuable input on the project.
EO and DW designed the study with significant input from BH. DW and JE performed the study. EO and DW wrote the manuscript with comments and edits from BH, JE, and members of the Developmental Exposure to Alcohol Research Center (DEARC).
This work was supported by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) via the Developmental Exposure to Alcohol Research Center (DEARC) P50AA017823-10.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no competing interests.
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