A73-10 Defining the Interactome of Igsf3 in Distal Lung Cells

Abstract Rationale Immunoglobulin superfamily member 3 (IGSF3) is a transmembrane protein with roles in cell adhesion, migration and cancer metastasis1 and predicted influence in cellular trafficking and membrane organization. Yet its biological function in the lung remains largely uncharacterized. Its decreased expression in small airways in cigarette smoke exposed mice2 suggests a role in maintaining alveolar structure and barrier integrity, processes disrupted in chronic obstructive pulmonary disease (COPD) and emphysema. We hypothesize that identification of the molecular interactors of IGSF3 in distal lung cells will show cellular trafficking, membrane organizational influence, and elucidate the mechanistic influence of IGSF3 on pathogenesis of chronic lung diseases such as COPD and Emphysema. Methods BioID proximity-dependent biotinylation and co-immunoprecipitation (co-IP) was performed on human small airway epithelial (HSAEC-KT), Human small airway basal cell ( NSABCi NS1.1) and microvascular endothelial cells (HULEC-5A). BioID detected transient or proximal associations analyzed by targeted proteomic analysis, co-IP identified stable complexes validated by immunoblotting. Immunoblotting and Immunocytochemistry confirmed co-localization and expression of IGSF3 and interactors in cells exposed to cigarette smoke extract (CSE, 2 %) and air control ( AC). Additionally, IGSF3 and identified interactor expression was characterized by transcriptomic analysis of RNA-seq of healthy, COPD, and COPD-PH lungs. Results Mass spectrometry identified several IGSF3-associated protein interactors confirmed by co-IP, including γ-glutamyltransferase (GGT) in HULEC cells, the LC3 fragment of endorepellin (C-terminal domain of HSPG2/perlecan), heterogeneous ribonucleoprotein (HNRNP) and tetraspanin-15 (TSPAN15) in HSAEC1-KT and NSABCi NS1.1 . IGSF3 co-localization with TSPAN15 at the plasma membrane was seen to be induced by CSE exposure in NSABCi NS1.1 cells. Conclusions This work provides the first molecular characterization of IGSF3-associated proteins in the human lung, positioning IGSF3 as a scaffold at the membrane-matrix interface that bridges adhesion, trafficking, and signaling pathways. These interactions link IGSF3 to extracellular matrix remodeling, vesicular trafficking, and membrane organization, pathways relevant to alveolar stability and endothelial injury in COPD. Understanding IGSF3’s interactome may reveal new mechanisms driving alveolar destabilization, endothelial dysfunction, and tissue remodeling in COPD and emphysema. 1 Ping Sheng et al, Annual Translational medicine 20202 Kelly Schweitzer et al , JCI insight 2020 This abstract is funded by: DoD W81XWH-22-1-0255