{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nSelenoprotein I (SELENOI), also known as ethanolamine phosphotransferase 1 (EPT1), functions as a key enzyme in the Kennedy pathway by catalyzing the final step of phosphatidylethanolamine (PE) synthesis. It transfers the ethanolamine phosphate group from CDP‑ethanolamine to lipid acceptors such as 1,2‑diacylglycerol or 1‑alkyl‑2‑acylglycerol to generate diacyl‐PE or plasmenyl‐PE, respectively. Disruption of this enzymatic activity due to mutations in SELENOI has been associated with neurodegenerative conditions such as hereditary spastic paraplegia, indicating the enzyme’s critical role in maintaining the integrity of lipid membranes in neuronal cells."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "\n \nDisruption of SELENOI activity has broader implications for neurodevelopment and immune cell function. Loss‐of‑function variants are linked to a spectrum of neurological deficits—including motor dysfunction, impaired myelination, sensorineural impairments, and brain atrophy—and studies have demonstrated that SELENOI plays an essential role in metabolic reprogramming during T cell activation and differentiation. These findings highlight the indispensable nature of SELENOI in both central nervous system physiology and in modulating the homeostasis of Ether‐linked phospholipids."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "3", "end_ref": "5"}]}, {"type": "t", "text": "\n \nBeyond its canonical role in phospholipid biosynthesis, SELENOI is expressed in multiple cellular compartments—including the nucleus, cytoplasm, and endoplasmic reticulum—and may contribute to cellular antioxidant responses and stress regulation. Its unique incorporation of a selenocysteine residue, although not directly involved in its transferase reaction, points to additional functions such as modulation of tumorigenesis and adipocyte differentiation. Regulation by factors such as dietary selenium intake further underscores the protein’s multifaceted impact on cell physiology and disease processes."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "6", "end_ref": "8"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Mustafa Y Ahmed, Aisha Al-Khayat, Fathiya Al-Murshedi, et al. 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