{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nRecent evidence has identified TRABD2A—as exemplified by the TIKI1 protein described in one study—as a transmembrane protease that posttranslationally inactivates secreted Wnt morphogens. By cleaving eight amino‐terminal residues of the Wnt ligand, TRABD2A triggers oxidation‐induced oligomerization that preserves secretion while greatly diminishing receptor binding. This targeted inactivation of Wnt signals is essential for proper head formation during embryogenesis, revealing a mechanism whereby extracellular morphogen activity is tightly regulated during development."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn contrast to the direct modulation of Wnt signaling by TRABD2A, a broad array of studies has delineated how receptor‐mediated cascades—often initiated by lipid signals such as lysophosphatidic acid—control diverse cellular processes. Investigations have shown that GPCRs, including various LPA receptor subtypes, orchestrate critical pathways governing cell survival, apoptosis, DNA repair, and differentiation in tissues ranging from the kidney and lung to the central nervous system and hematopoietic system. These studies underscore that extracellular signal modulation via receptor binding, proteolytic processing, and interactions with macromolecular complexes is a central strategy in both development and disease."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "2", "end_ref": "9"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nTogether, these insights illustrate that while TRABD2A functions as a Wnt-specific protease required for embryonic patterning, it is set within a wider biological context in which extracellular signals are fine-tuned through receptor activation, enzymatic modification, and downstream cascade activation. The emerging picture emphasizes that both proteolytic inactivation (as mediated by TRABD2A/TIKI1 in the Wnt pathway) and modulation by lipid-activated GPCRs—whose roles extend to DNA repair, fibrosis, immune regulation, and neural functions—are critical for ensuring proper development, maintaining tissue homeostasis, and modulating pathological responses. This integrated understanding opens promising avenues for therapeutic interventions targeting these extracellular signaling pathways."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "10", "end_ref": "21"}]}, {"type": "t", "text": ""}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Xinjun Zhang, Jose Garcia Abreu, Chika Yokota, et al. 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