{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nPI4KA (phosphatidylinositol‐4‐kinase IIIα) is a pivotal lipid kinase that catalyzes the generation of phosphatidylinositol 4‐phosphate (PI4P), a critical precursor for the synthesis of other phosphoinositides. Multiple independent studies have demonstrated that its enzymatic activity is indispensable for the replication of hepatitis C virus (HCV). In HCV‐infected cells, PI4KA is directly engaged by the viral nonstructural protein NS5A, which binds and stimulates its kinase activity, leading to dramatic increases in cytoplasmic PI4P and the appropriate formation of membranous replication compartments. Genetic silencing or pharmacological inhibition of PI4KA consistently impairs HCV RNA replication and virus release, and mapping studies have identified a conserved NS5A–PI4KA interaction domain that regulates NS5A phosphorylation and replication complex integrity."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "7"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its viral‐related roles, PI4KA is central to the regulation of normal cellular signaling. It maintains plasma membrane phosphoinositide pools by generating PI4P that serves as a substrate for PI(4,5)P2 synthesis—an essential lipid for receptor activation, Ca²⁺ signaling, and membrane trafficking. Studies employing both pharmacological inhibitors and genetic approaches have shown that even subtle alterations in PI4KA activity can perturb PI4P levels, thereby affecting downstream signaling pathways. In addition, PI4KA participates in multikinase scaffold complexes (for example, with IQGAP1) that coordinate sequential phosphorylation events culminating in the generation of other lipid second messengers critical for cell growth and survival."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "8", "end_ref": "12"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nEmerging evidence also implicates PI4KA in human disease and oncogenic signaling. Genetic studies have associated sequence variants in the PI4KA gene (also known as PIK4CA) with neuropsychiatric conditions such as schizophrenia, while biallelic mutations can result in complex syndromes encompassing neurological impairment, immunodeficiency, and intestinal abnormalities. In cancer, both aberrant PI4KA expression and the production of its lipid product have been linked to enhanced tumor growth and metastatic behavior through interactions with chemokine receptors and intracellular adaptor proteins. In addition, noncoding RNAs derived from the PI4KA locus appear to act as oncogenic factors in certain carcinomas by modulating microRNA networks."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "13", "end_ref": "19"}]}, {"type": "t", "text": ""}]}]}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Simon Reiss, Ilka Rebhan, Perdita Backes, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "Hepatitis C virus stimulates the phosphatidylinositol 4-kinase III alpha-dependent phosphatidylinositol 4-phosphate production that is essential for its replication."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Virol (2011)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1128/JVI.00059-11"}], "href": "https://doi.org/10.1128/JVI.00059-11"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "21697487"}], "href": "https://pubmed.ncbi.nlm.nih.gov/21697487"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Yun-Sook Lim, Soon B Hwang "}, {"type": "b", "children": [{"type": "t", "text": "Hepatitis C virus NS5A protein interacts with phosphatidylinositol 4-kinase type IIIalpha and regulates viral propagation."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Biol Chem (2011)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1074/jbc.M110.194472"}], "href": "https://doi.org/10.1074/jbc.M110.194472"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "21297162"}], "href": "https://pubmed.ncbi.nlm.nih.gov/21297162"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Simon Reiss, Christian Harak, Inés Romero-Brey, et al. 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