{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nSarcospan (SSPN) is a small transmembrane protein that serves as a critical component of the dystrophin‐glycoprotein complex (DGC) and the utrophin‐glycoprotein complex (UGC) in muscle. It regulates key signaling pathways—most notably the Akt pathway—to control utrophin expression and influences the glycosylation of α‑dystroglycan, thereby enhancing the delivery and stabilization of utrophin and dystroglycans at the cell surface. In dystrophin-deficient muscle models, this upregulation and improved trafficking promote cell-matrix adhesion and facilitate efficient muscle regeneration."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its role in skeletal muscle repair, SSPN is essential for cardiac muscle integrity. Loss of SSPN has been shown to decrease the abundance of adhesion complexes, impair laminin binding, and disrupt Ca2+ handling—factors that contribute to increased susceptibility to contraction-induced injury and enhanced infarct size during ischemia-reperfusion injury. Furthermore, compensatory regulation via integrin modulation by SSPN helps preserve extracellular matrix attachment and force transmission in both normal and dystrophic contexts."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "4", "end_ref": "6"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nAdditional work indicates that SSPN contributes to cellular survival under environmental stress such as hypoxia. Its downregulation correlates with increased cell death in hypoxic conditions, while overexpression of the native mouse SSPN variant safely improves the stability of the sarcolemma and ameliorates dystrophic pathology in experimental models. Although the studies provided do not directly address “NLRP2B,” the comprehensive characterization of SSPN functions—including its roles in signal transduction, protein trafficking, and membrane stabilization—provides an important framework for understanding similar transmembrane proteins involved in maintaining muscle integrity."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "7", "end_ref": "9"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Dan Zhou, Jiyi Wang, Matthew A Zapala, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "Sarcospan-dependent Akt activation is required for utrophin expression and muscle regeneration."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Cell Biol (2012)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1083/jcb.201110032"}], "href": "https://doi.org/10.1083/jcb.201110032"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "22734004"}], "href": "https://pubmed.ncbi.nlm.nih.gov/22734004"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Jamie L Marshall, Jennifer Oh, Eric Chou, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Sarcospan integration into laminin-binding adhesion complexes that ameliorate muscular dystrophy requires utrophin and α7 integrin."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Hum Mol Genet (2015)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1093/hmg/ddu615"}], "href": "https://doi.org/10.1093/hmg/ddu615"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "25504048"}], "href": "https://pubmed.ncbi.nlm.nih.gov/25504048"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Jamie L Marshall, Eric Chou, Jennifer Oh, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Dystrophin and utrophin expression require sarcospan: loss of α7 integrin exacerbates a newly discovered muscle phenotype in sarcospan-null mice."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Hum Mol Genet (2012)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1093/hmg/dds271"}], "href": "https://doi.org/10.1093/hmg/dds271"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "22798625"}], "href": "https://pubmed.ncbi.nlm.nih.gov/22798625"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Michelle S Parvatiyar, Jamie L Marshall, Reginald T Nguyen, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Sarcospan Regulates Cardiac Isoproterenol Response and Prevents Duchenne Muscular Dystrophy-Associated Cardiomyopathy."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Am Heart Assoc (2015)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1161/JAHA.115.002481"}], "href": "https://doi.org/10.1161/JAHA.115.002481"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "26702077"}], "href": "https://pubmed.ncbi.nlm.nih.gov/26702077"}]}, {"type": "r", "ref": 6, "children": [{"type": "t", "text": "Hyun Seok Hwang, Aida Rahimi Kahmini, Julia Prascak, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Sarcospan Deficiency Increases Oxidative Stress and Arrhythmias in Hearts after Acute Ischemia-Reperfusion Injury."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Int J Mol Sci (2023)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.3390/ijms241411868"}], "href": "https://doi.org/10.3390/ijms241411868"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "37511627"}], "href": "https://pubmed.ncbi.nlm.nih.gov/37511627"}]}, {"type": "r", "ref": 7, "children": [{"type": "t", "text": "Elizabeth M Gibbs, Jamie L Marshall, Eva Ma, et al. "}, {"type": "b", "children": [{"type": "t", "text": "High levels of sarcospan are well tolerated and act as a sarcolemmal stabilizer to address skeletal muscle and pulmonary dysfunction in DMD."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Hum Mol Genet (2016)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1093/hmg/ddw356"}], "href": "https://doi.org/10.1093/hmg/ddw356"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "27798107"}], "href": "https://pubmed.ncbi.nlm.nih.gov/27798107"}]}, {"type": "r", "ref": 8, "children": [{"type": "t", "text": "Angela K Peter, Gaynor Miller, Joana Capote, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Nanospan, an alternatively spliced isoform of sarcospan, localizes to the sarcoplasmic reticulum in skeletal muscle and is absent in limb girdle muscular dystrophy 2F."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Skelet Muscle (2017)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1186/s13395-017-0127-9"}], "href": "https://doi.org/10.1186/s13395-017-0127-9"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "28587652"}], "href": "https://pubmed.ncbi.nlm.nih.gov/28587652"}]}, {"type": "r", "ref": 9, "children": [{"type": "t", "text": "Elizabeth M Gibbs, Jackie L McCourt, Kara M Shin, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Loss of sarcospan exacerbates pathology in mdx mice, but does not affect utrophin amelioration of disease."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Hum Mol Genet (2021)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1093/hmg/ddaa264"}], "href": "https://doi.org/10.1093/hmg/ddaa264"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "33432327"}], "href": "https://pubmed.ncbi.nlm.nih.gov/33432327"}]}]}]}