{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Lysophosphatidic acid receptor 5 (LPA₅), originally identified as GPR92, is an atypical G protein–coupled receptor that binds lysophosphatidic acid (LPA) with high affinity and mediates signaling via coupling to G_q and G_12/13 proteins. Activation of LPA₅ induces intracellular calcium mobilization, cAMP production, and downstream events that modulate cell shape, motility, and cytoskeletal organization. Structure–function studies have delineated key residues within its ligand‐binding pocket that are critical for receptor activation by LPA and related lysophospholipid agonists."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In the sensory nervous system, LPA₅ is highly expressed in dorsal root ganglia and spinal cord neurons where its activation contributes to nociceptive signaling; genetic deletion of LPA₅ results in reduced neuropathic pain and diminished activation of pain‐associated transcription factors, underscoring its role in pain hypersensitivity."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "5", "end_ref": "7"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In immune cells such as human mast cells and B lymphocytes, LPA₅ is the predominant receptor mediating LPA‐induced Ca²⁺ flux and chemokine release; notably, engagement of LPA₅ negatively regulates B cell receptor signaling and attenuates antigen‐induced activation, thereby modulating inflammatory and adaptive immune responses."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n In the context of tumor progression, cell‐autonomous LPA₅ signaling in melanoma cells has been shown to suppress invasion, whereas its expression in host tissues contributes to the seeding of metastasis, highlighting a complex, context‐dependent role in cancer biology."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Furthermore, LPA₅ expressed in intestinal epithelial cells plays a critical role in stimulating Na⁺/H⁺ exchanger 3 activity and promoting fluid absorption, a function that may have therapeutic potential in the treatment of diarrheal diseases."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "12"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Overall, LPA₅ is a multifunctional receptor that orchestrates diverse biological responses—including modulation of pain, immune regulation, control of tumor cell invasion, and regulation of fluid homeostasis—thereby representing a promising target for therapeutic intervention in several pathological conditions.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Chang-Wook Lee, Richard Rivera, Shannon Gardell, et al. 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