L1 coupling to ankyrin and the spectrin‐actin cytoskeleton modulates ethanol inhibition of L1 adhesion and ethanol teratogenesis

Abstract

Ethanol causes fetal alcohol spectrum disorders (FASDs) partly by inhibiting cell adhesion mediated by the L1 neural cell adhesion molecule. Ethanol interacts with an alcohol binding pocket in the L1 extracellular domain (ECD), and dephosphorylation of S1248 in the L1 cytoplasmic domain (CD) renders L1 adhesion insensitive to inhibition by ethanol (L1 insensitive). The mechanism underlying this inside-out signaling is unknown. Here we show that phosphorylation of the human L1-CD at S1152, Y1176, S1181, and S1248 renders L1 sensitive to ethanol by promoting L1 coupling with ankyrin-G and the spectrin-actin cytoskeleton. Knockdown of ankyrin-G or L1 mutations that uncouple L1 from ankyrin reduce L1 sensitivity to ethanol, but not methanol, consistent with a small conformational change in the extracellular alcohol binding pocket. Phosphorylation of Y1176 and ankyrin-G coupling with L1 are higher in NIH/3T3 clonal cell lines in which ethanol inhibits L1 adhesion than in ethanol-resistant NIH/3T3 clonal cell lines. Similarly, phosphorylation of Y1176 is higher in C57BL/6J mice that are sensitive to ethanol teratogenesis than in ethanol resistant C57BL/6N mice. Finally, polymorphisms in genes that encode ankyrin-G and p90rsk, a kinase that phosphorylates S1152, are linked to facial dysmorphology in children with heavy prenatal ethanol exposure. These findings indicate that genes that regulate L1 coupling to ankyrin may influence susceptibility to FASD.-Dou, X., Menkari, C., Mitsuyama, R., Foroud, T., Wetherill, L., Hammond, P., Suttie, M., Chen, X., Chen, S.-Y., Charness, M. E., Collaborative Initiative on Fetal Alcohol Spectrum Disorders. L1 coupling to ankyrin and the spectrin-actin cytoskeleton modulates ethanol inhibition of L1 adhesion and ethanol teratogenesis. FASEB J. 32, 1364FASEB J. 32, -1374FASEB J. 32, (2018. www.fasebj.orgFetal alcohol spectrum disorder (FASD) is the most common preventable cause of intellectual disability (1, 2). At the most severe end of the spectrum are children with fetal alcohol syndrome (FAS), a disorder marked by typical facial dysmorphology, pre-and/or postnatal growth deficiency, neurobehavioral impairment, and structural or functional brain abnormalities. The facial dysmorphology of FAS arises from alcohol exposure during gastrulation, but ethanol can disrupt brain development throughout gestation (3). Consequently, many children with prenatal alcohol exposure and normal facial morphology still demonstrate cognitive, behavioral, and social impairment (2). Although FASD is preventable, fetal alcohol exposure still occurs frequently before pregnancy recognition and often later in gestation, despite the known risks (4).Genetic factors modify the risk of FASD (5). Ethanol teratogenicity differs markedly in genetically related animal strains (6), and human monozygotic twins demonstrate higher concordance for FAS than dizygotic twins (7).

Murine Models for the Study of Fetal Alcohol Spectrum Disorders: An Overview

“…For example, the highly sialylated form of NCAM is overexpressed after ethanol exposure but the NCAM 180 and NCAM 140 isoforms appear down-regulated in a rat model (137). Other studies in animal models (mice and rats) have shown down-regulation of L1 following ethanol exposure (134,138).…”

“…PAE affects the expression levels of synaptic proteins such as synapsin 1 and of other proteins of the pre-synaptic (GAP-43, synaptophysin, synaptotagmin) or post-synaptic machinery (MAP 2 and neurogranin). Moreover, ethanol interferes with the function of adhesion molecules such as NCAM (in chick embryo model) ( 133 ) and L1 (in mouse model) ( 134 ) involved in cell-cell interactions. During the neural processes of migration and morphogenesis, both proteins are involved in the organization and function of synaptic networks, which determine neuronal plasticity.…”

Clinical presentation, diagnosis, and management of fetal alcohol spectrum disorder

“…76,[80][81][82][83] Alcohol disrupts neural cell migration and axonal pathfinding by blocking cell adhesion and axon outgrowth mediated by the L1 neural cell adhesion molecule. 84 Of note, mutations in the human L1 gene cause dysgenesis of the corpus callosum, hydrocephalus, and cerebellar dysplasia, mirroring some of the neuropathological abnormalities of FAS. Alcohol also alters craniofacial and brain development by disrupting PDGFRA and its downstream signaling elements, PI3K and mTOR.…”

“…85 Genetic polymorphisms in PDGFRA and in genes that regulate L1 sensitivity to ethanol are associated with craniofacial and brain dysmorphology in humans. 84,85 Developmental Course FASD has not been well studied in adults and the phenotype is older adults is unknown. Some adults received their diagnoses during childhood; however, the high prevalence of FASD and high rates of misdiagnosis in children 10 suggest that FASD is often undiagnosed in adults.…”

The role of spectrin in cell adhesion and cell–cell contact

“…67 Also, it has been recently documented that L1 coupling to ankyrin and therefore to the spectrin-actin skeleton modulates ethanol inhibition of L1 adhesion and ethanol teratogenesis. 80 Furthermore, aII-spectrin interacts with the protein 14-3-3, which is engaged in neuronal migration and synaptic plasticity. This interaction works as a positive/negative switch in NCAM-dependent neurite outgrowth.…”