Invited Review ArticleCardiac Titin and Heart DiseaseLeWinter, Martin M. MD*; Granzier, Henk L. PhD†,‡Author Information *Cardiology Unit, Fletcher Allen Health Care, Department of Medicine, University of Vermont, Burlington, VT; and †Sarver Molecular Cardiovascular Research Program, and ‡Department of Physiology, University of Arizona, Tucson, AZ. Reprints: Martin M. LeWinter, MD, Cardiology Unit, Fletcher Allen Health Care, Department of Medicine, University of Vermont, 111 Colchester Avenue, Burlington, VT 05401 (e-mail: email@example.com). Supported by National Institutes of Health grants R01 HL062881 (H.L.G.) and RO1 HL089944 (M.M.L.) and a gift from Allan and Alfie Norville to H. L. Granzier. The authors report no conflicts of interest. Received May 02, 2013 Accepted July 24, 2013 Journal of Cardiovascular Pharmacology: March 2014 - Volume 63 - Issue 3 - p 207-212 doi: 10.1097/FJC.0000000000000007 Buy Metrics Abstract Abstract: The giant sarcomeric protein titin is a key determinant of myocardial passive stiffness and stress-sensitive signaling. Titin stiffness is modulated by isoform variation, phosphorylation by protein kinases, and, possibly, oxidative stress through disulfide bond formation. Titin has also emerged as an important human disease gene. Early studies in patients with dilated cardiomyopathy (DCM) revealed shifts toward more compliant isoforms, an adaptation that offsets increases in passive stiffness based on the extracellular matrix. Similar shifts are observed in heart failure with preserved ejection fraction. In contrast, hypophosphorylation of PKA/G sites contributes to a net increase in cardiomyocyte resting tension in heart failure with preserved ejection fraction. More recently, titin mutations have been recognized as the most common etiology of inherited DCM. In addition, some DCM-causing mutations affect RBM20, a titin splice factor. Titin mutations are a rare cause of hypertrophic cardiomyopathy and also underlie some cases of arrhythmogenic right ventricular dysplasia. Finally, mutations of genes encoding proteins that interact with and/or bind to titin are responsible for both DCM and hypertrophic cardiomyopathy. Targeting titin as a therapeutic strategy is in its infancy, but it could potentially involve manipulation of isoforms, posttranslational modifications, and upregulation of normal protein in patients with disease-causing mutations. © 2014 by Lippincott Williams & Wilkins.