{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nCPI‐17, encoded by the PPP1R14A gene, is a pivotal endogenous inhibitor of myosin light chain phosphatase (MLCP) that modulates smooth muscle contraction and Ca²⁺ sensitivity. Its discovery in human, mouse, and rat tissues revealed a high degree of conservation and tissue‐specific expression."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": " In permeabilized smooth muscle preparations, phosphorylation of CPI‐17 at threonine 38 by protein kinase C (PKC) is critical for enhancing Ca²⁺ sensitization and contractile responses."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": " In models of intestinal inflammation, downregulation of CPI‐17 by proinflammatory cytokines such as TNF‐α and IL‐1β is associated with reduced contractility and motility disturbances"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": ", while developmental studies indicate that CPI‐17 expression is tightly regulated during smooth muscle differentiation and is diminished in vascular neointimal lesions."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nWithin vascular smooth muscle cells, CPI‐17 acts as a linchpin integrating multiple signaling pathways that regulate contractility. Under diabetic conditions, high glucose induces a PKC‐dependent upregulation of calcium‐independent phospholipase A₂β, which activates the RhoA/ROCK/CPI‐17 cascade, resulting in vascular hypercontractility."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": " In parallel, while Rho kinase–mediated inhibition of MLCP is essential for force generation, CPI‐17 further fine‐tunes Ca²⁺ sensitivity."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": " In colitis, alterations in colonic smooth muscle contractility implicate the PKC pathway—likely involving CPI‐17—in the development of hypercontractile responses."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": " Moreover, during vascular smooth muscle differentiation, CPI‐17 contributes to the regulation of myocardin expression through effects on transcription factors such as MEF2C."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": " In the urinary bladder, upregulation of CPI‐17 via the concerted action of GATA‐6 and NF‑κB modulates contractile function and is implicated in smooth muscle remodeling under pathological conditions (e.g., benign prostatic hyperplasia)."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nThe physiological significance of CPI‐17 is further underscored by its critical role in maintaining vascular tone and blood pressure. In septic conditions, inflammatory mediators trigger a decrease in CPI‐17 expression, contributing to vascular hypocontractility and vasodilatory shock."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}]}, {"type": "t", "text": " Genetic studies using CPI‐17 knockout and phospho‐resistant mouse models demonstrate that loss of functional, phosphorylated CPI‐17 results in blunted vasoconstrictor responses and lower mean blood pressure."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "11"}]}, {"type": "t", "text": " Furthermore, lipopolysaccharide (LPS)–induced, TNF‐mediated transcriptional repression of CPI‐17 via KLF4 and HDAC recruitment provides a mechanistic link between inflammatory signaling and impaired smooth muscle contraction."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "12"}]}, {"type": "t", "text": " In contrast, obesity‐related hypertension is associated with an upregulation of CPI‐17 that enhances GPCR/PKC-mediated calcium sensitization, thereby contributing to increased vascular contractility and elevated blood pressure."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "13"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Z Li, L Yu, Y Zhang, et al. 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