Astrocyte–neuron subproteomes and obsessive–compulsive disorder mechanisms

Abstract

Astrocytes and neurons extensively interact in the brain. Identifying astrocyte and neuron proteomes is essential for elucidating the protein networks that dictate their respective contributions to physiology and disease. Here we used cell-specific and subcompartment-specific proximity-dependent biotinylation1 to study the proteomes of striatal astrocytes and neurons in vivo. We evaluated cytosolic and plasma membrane compartments for astrocytes and neurons to discover how these cells differ at the protein level in their signalling machinery. We also assessed subcellular compartments of astrocytes, including end feet and fine processes, to reveal their subproteomes and the molecular basis of essential astrocyte signalling and homeostatic functions. Notably, SAPAP3 (encoded by Dlgap3), which is associated with obsessive–compulsive disorder (OCD) and repetitive behaviours2–8, was detected at high levels in striatal astrocytes and was enriched within specific astrocyte subcompartments where it regulated actin cytoskeleton organization. Furthermore, genetic rescue experiments combined with behavioural analyses and molecular assessments in a mouse model of OCD4 lacking SAPAP3 revealed distinct contributions of astrocytic and neuronal SAPAP3 to repetitive and anxiety-related OCD-like phenotypes. Our data define how astrocytes and neurons differ at the protein level and in their major signalling pathways. Moreover, they reveal how astrocyte subproteomes vary between physiological subcompartments and how both astrocyte and neuronal SAPAP3 mechanisms contribute to OCD phenotypes in mice. Our data indicate that therapeutic strategies that target both astrocytes and neurons may be useful to explore in OCD and potentially other brain disorders.

Astrocyte ensheathment of calyx‐forming axons of the auditory brainstem precedes accelerated expression of myelin genes and myelination by oligodendrocytes

“…Development of methods to identify mRNA localized to axon wraps would reveal more specifically a functional unit, which may include structural, cell adhesion, and even ion channels. Proteomic analysis utilizing known molecules in specialized structures, such as end‐feet (Aquaporin4; Aqp4) and fine processes (Ezrin; Ezr), as promoters for genetically targeted biotin ligase identified astrocyte subproteomes in these biological compartments (Soto et al., 2023). Both Aqp4 and Ezr are differentially expressed in the MNTB from P0 to P6 (Kolson et al., 2016), consistent with formation of the vasculature during this time (Brandebura et al., 2022), and subproteomic analysis in the fine processes of astrocytes may identify cell adhesion molecules relevant to the extensive ensheathment we observed on calyceal axons.…”

“…Proteomic analysis utilizing known molecules in specialized structures, such as end-feet (Aquaporin4; Aqp4) and fine processes (Ezrin; Ezr), as promoters for genetically targeted biotin ligase identified astrocyte subproteomes in these biological compartments (Soto et al, 2023).…”

Synaptic proteomics decode novel molecular landscape in the brain

“…Under lipopolysaccharide (LPS)-stimulated inflammatory conditions, more than 500 proteins showed differential abundance out of the 2,350 identified, demonstrating an increase in inflammatory proteins (Il1a, Irg1, Oasl1) and a decrease in anti-inflammatory proteins (Arg1, Mgl2) ( Sunna et al, 2023 ). Moreover, the proteome specific to different cell types and subcellular locations was assessed using AAV vectors carrying either cytosolic-BioID2 or plasma membrane-BioID2 in vivo ( Soto et al, 2023 ) ( Figure 1B ; Table 1 ). They were expressed in mouse striatal neurons (AAV- hSynI -BioID2 and AAV- hSynI -Lck-BioID2) and astrocytes (AAV- GfaABC 1 D -BioID2 and AAV- GfaABC 1 D -Lck-BioID2) ( Soto et al, 2023 ).…”

Proteomic profiling of interferon‐responsive reactive astrocytes in rodent and human

“…In addition to robust changes in gene expression, morphology, and function (Hasel et al, 2023), these heterogeneous populations of reactive astrocytes are now beginning to be defined at the protein and lipid level (Guttenplan et al, 2021;Soto et al, 2023). These additional layers of reactive astrocyte complexity are helping to expand our understanding of the changes associated with reactive astrocytes and whether they hinder or support the CNS environment.…”

“…In response to pathogenic insults, disease, or following infection and injury, homeostatic astrocytes undergo a transformation called “reactivity” that causes profound changes to their molecular signature and function (Han et al, 2021). In addition to robust changes in gene expression, morphology, and function (Hasel et al, 2023), these heterogeneous populations of reactive astrocytes are now beginning to be defined at the protein and lipid level (Guttenplan et al, 2021; Soto et al, 2023). These additional layers of reactive astrocyte complexity are helping to expand our understanding of the changes associated with reactive astrocytes and whether they hinder or support the CNS environment.…”