Integrin β3 Haploinsufficiency Modulates Serotonin Transport and Antidepressant-Sensitive Behavior in Mice

Abstract

Converging lines of evidence have identified genetic interactions between the serotonin transporter (SERT) gene and ITGB3, which encodes the β3 subunit that forms the αIIbβ3 and αvβ3 integrin receptor complexes. Here we examine the consequences of haploinsufficiency in the mouse integrin β3 subunit gene (Itgb3) on SERT function and selective 5-hydroxytryptamine (5-HT) reuptake inhibitor (SSRI) effectiveness in vivo. Biochemical fractionation studies and immunofluorescent staining of murine brain slices reveal that αvβ3 receptors and SERTs are enriched in presynaptic membranes from several brain regions and that αvβ3 colocalizes with a subpopulation of SERT-containing synapses in raphe nuclei. Notably, we establish that loss of a single allele of Itgb3 in murine neurons is sufficient to decrease 5-HT uptake by SERT in midbrain synaptosomes. Pharmacological assays to elucidate the αvβ3-mediated mechanism of reduced SERT function indicate that decreased integrin β3 subunit expression scales down the population size of active SERT molecules and, as a consequence, lowers the effective dose of SSRIs. These data are consistent with the existence of a subpopulation of SERTs that are tightly modulated by integrin αvβ3 and significantly contribute to global SERT function at 5-HT synapses in the midbrain. Importantly, our screen of a normal human population for single nucleotide polymorphisms in human ITGB3 identified a variant associated with reductions in integrin β3 expression levels that parallel our mouse findings. Thus, polymorphisms in human ITGB3 may contribute to the differential responsiveness of select patients to SSRIs.

High-risk Autism Spectrum Disorder Utah pedigrees: a novel Shared Genomic Segments analysis

“…Also in family 10001, seven affected, and one unaffected sibling, share the segment on chromosome 17q21.32 containing integrin subunit beta 3 ( ITGB3 ), which has been previously associated with ASD [46–53], although not in a cohort of Irish ASD cases [54]. Considered by ASD@Princeton to be a known ASD gene, ITGB3 plays a role in cell adhesion, and regulates serotonin levels through an interaction with the serotonin transporter [55]. Interestingly, the lone affected case that does not share this segment is the MZ twin.…”

Mice lacking integrin β3 expression exhibit altered response to chronic stress

“…Integrin β3 influences synaptic plasticity via AMPA and NMDA receptor trafficking mechanisms ( Bahr, 2000 , Bernard-Trifilo et al., 2005 , Cingolani et al., 2008 , Juhasz et al., 2008 , Lin et al., 2003 , Pozo et al., 2012 ), which are involved in the functional and structural alterations observed after exposure to chronic stress ( Christian et al., 2011 , Kallarackal et al., 2013 ). Integrin β3 also influences midbrain high-affinity 5-HT reuptake via the serotonin transporter (SERT) ( Mazalouskas et al., 2015 , Whyte et al., 2014 ), and mice lacking SERTs display enhanced sensitivity to repeated stress, which are associated with altered dendritic morphology of pyramidal neurons in the prefrontal cortex ( Wellman et al., 2007 ). Our neurochemical studies revealed increased midbrain levels of 5-HT and its metabolite, 5-HIAA, in mice lacking β3 expression, which were not influenced by UCMS.…”

“…Cell adhesion molecules, such as integrins, are ideally poised to regulate many of these processes, as many are involved in apoptosis, dendritic reorganization, the regulation of synaptic connectivity, and receptor localization ( Kerrisk and Koleske, 2013 , Scheiffele et al., 2000 ). Integrins are particularly enriched in synaptic regions ( Bahr et al., 1997 , Kramar et al., 2002 , Mazalouskas et al., 2015 , Nishimura et al., 1998 ), where they participate in synaptic development, maintenance and the cytoskeletal rearrangements that accompany synaptic activity ( Bahr, 2000 , Chavis and Westbrook, 2001 , Hama et al., 2004 , Karanian et al., 2005 , Nikonenko et al., 2003 ). Integrin expression and downstream signaling are modulated by antidepressant exposure, implying that integrins are involved in mood regulation ( Malki et al., 2012 , Oved et al., 2013 ).…”

“…The vitronectin receptor, integrin αvβ3, bi-directionally connects the extracellular matrix (ECM) with intracellular signaling pathways ( Hynes, 2002 ). Many integrin subunits, including αvβ3, are expressed at hippocampal, midbrain, and cortical synapses in the brain ( Cingolani and Goda, 2008 , Cingolani et al., 2008 , Mazalouskas et al., 2015 ). Integrin αvβ3 modulates both serotonergic and glutamatergic neurotransmission in the central nervous system by modifying pre-and post-synaptic protein function ( Bisaz and Sandi, 2012 , Cingolani and Goda, 2008 , Whyte et al., 2014 ).…”

Correction of β3 integrin haplo-insufficiency by CRISPRa normalizes cortical network activity

“…Ten days post-infection, cultures were fixed for 8 min with 4% PFA/4% sucrose at room temperature (RT), treated for 10 min at 50°C with a sodium citrate solution (10 mM tri-sodium citrate dihydrate, pH 6.0, 0.05% Tween-20) to retrieve the β3 integrin antigen (Mazalouskas et al, 2015) and permeabilized for 10 min at RT with 0.1% TritonX-100. β3 integrin staining was revealed using a rabbit monoclonal anti-integrin β3 (1: Ai,coloc is calculated as ∑i Ai but only for pixels where also the second channel B is above threshold).…”