Introduction: Atrial Fibrillation (AF) is one of the most commonly occurring arrhythmias and is associated with an increased risk of stroke, heart failure and significantly higher morbidity and mortality rates. The pathophysiology of AF is not well understood.  Lysosomes are recognized as the major location for degradation of both intracellular and extracellular macromolecules and contain more than 50 identified acid hydrolases. The ability of lysosomes to act as Ca2+ stores and participate in calcium signaling processes is relatively understudied. Studies have investigated the role of lysosomal calcium channels in fundamental cellular processes and their involvement in disease mechanisms1. Understanding the role played by lysosomes in the mechanisms underlying AF is vital for the development of pharmacological therapies to treat AF. Methods: This study was carried out in accordance with the principles of the Basel Declaration and regulations of European directive 2010/63/EU. The local ethical board for animal experimentation of the Maastricht University approved the protocol. Goats were maintained in AF for 6 months. Following open chest sacrifice experiments (n=3 persistent AF and n=3 sham controls), left atrial tissue biopsies were swiftly snap frozen in liquid nitrogen. Samples were prepared for organelle proteomics using a method recently developed in our lab2. We performed label-free quantitative proteomics on tissue lysate (TL), endolysosome (EL) and mitochondria (Mito) fractions.   Results: Raw mass spectrometry data was obtained from label-free quantitative (LFQ) proteomics. The protein intensities were quantified and analysed using Perseus 1.6.15.0, and the differential experiment groups of AF vs Sham control displayed a 42.8% variability under principal component analysis. Significantly upregulated proteins were identified by volcano plot.     The major molecular networks were studied using Gene Ontology, KeGG, Panther and Cytoscape pathways. Confirmation of regulated lysosomal proteins discovered in proteomics were followed up with molecular techniques including Western blotting for Ras related protein 11 (RAB11), N-ethylmaleimide-sensitive factor (NSF), Glycogenin-1(GYG1) and lysosomal assays such as beta galactosidase and beta hexosaminidase. The EL fraction showed enrichment for EL specific proteins such as lysosomal alpha glucosidase (GAA), Clathrin light chain (CLTB), T-complex protein 1 subunit beta (CCT2), vacuolar protein-sorting-associated protein 25 (VPS25) and many more. Discussion: We observe in KEGG pathways analysis – mitochondrial TCA, OXPHOS, glycolysis and the AMPK pathway protein upregulation, highlighting that there could be an increase in ATP energy demand in AF. The upregulation of proteins in endocytosis and protein processing in endoplasmic reticulum suggest increased vesicular trafficking potentially to support the increased metabolic energetics and recycling of the cellular waste. However, the downregulation of autophago-lysosome fusion proteins such as dynein and dynamin indicate a possible disruption in the cellular degradation of macromolecules in the atrial cell during chronic AF. Further confirmation of P62, LC3 II/I ratio and whether they increase, indicating a blockage of autophago-lysosome and autolysosome fusion, is required. Our omics data provides evidence to support the role of the lysosome as an important intracellular organelle which may play a role in AF pathology.