{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nARH is a clathrin-associated adaptor protein that plays a central role in mediating the endocytosis of the low-density lipoprotein receptor (LDLR) in the liver. In vivo studies using ARH-deficient mice and clinical observations in patients with autosomal recessive hypercholesterolemia demonstrate that loss of ARH disrupts the internalization of LDLR, resulting in markedly decreased LDL clearance and consequent hypercholesterolemia—even though LDLR function appears normal in cultured cells. Furthermore, combined deficiencies in ARH and other adaptors such as Dab2 exacerbate these effects, underlining the critical role of ARH in cholesterol homeostasis."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nARH also contributes to the clearance of apoE‐containing lipoproteins. Models in which apoE or LDLR interactions are perturbed reveal that deficiencies in these interactions can lead to hypertriglyceridemia and improper plasma lipoprotein clearance, emphasizing ARH’s role in maintaining overall lipid balance in vivo."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nThe adaptor function of ARH is subject to modulation by gamma-secretase activity. Loss of presenilin function or the presence of Alzheimer’s disease–associated presenilin mutants can lead to the accumulation of ARH substrates, mistargeting of endocytic adaptor proteins, and altered levels of apolipoproteins—thereby establishing a link between ARH-mediated receptor endocytosis and neurodegenerative pathways."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn the kidney, ARH is integral to the regulation of potassium homeostasis by directly interacting with ROMK channels. By binding to ROMK via a variant NPXY signal, ARH recruits these channels to clathrin-coated pits, thereby modulating their endocytosis in response to dietary potassium changes. This function links endocytic trafficking with renal potassium excretion and electrolyte balance."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its role at the plasma membrane, ARH associates with centrosomal structures and components of the mitotic machinery. Its interactions with centrosomal proteins and dynein motor complexes, as well as its dynamic localization from the nuclear membrane to the kinetochores and spindle poles during mitosis, suggest that ARH is implicated in proper centrosome assembly and cytokinesis, thereby affecting cell cycle progression."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nARH function is further regulated by nitric oxide through posttranslational nitrosylation at specific cysteine residues. This modification is critical for ARH’s association with the AP-2 adaptor complex and the correct targeting of LDL-LDLR complexes to clathrin-coated pits. Consequently, nitric oxide levels can selectively influence ARH-dependent lipoprotein uptake without affecting other LDLR-mediated processes."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn the brain, ARH is widely expressed in neuronal populations, where it interacts with several proteins including amyloid precursor-like protein 1, multiple LDL receptor–related proteins, and GABA receptor–associated proteins. Moreover, ARH mRNA is present in axons, indicating that local synthesis of ARH might contribute to neuronal functions that extend beyond traditional lipoprotein metabolism—potentially impacting neurodevelopment and neurodegenerative processes."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": ""}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Christopher Jones, Robert E Hammer, Wei-Ping Li, et al. 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