Myopodin is an F-actin bundling protein with multiple independent actin-binding regions
- 9 December 2012
- journal article
- Published by Springer Science and Business Media LLC in Journal of Muscle Research and Cell Motility
- Vol. 34 (1), 61-69
- https://doi.org/10.1007/s10974-012-9334-5
Abstract
The assembly of striated muscle myofibrils is a multistep process in which a variety of proteins is involved. One of the first and most important steps in myofibrillogenesis is the arrangement of thin myofilaments into ordered I-Z-I brushes, requiring the coordinated activity of numerous actin binding proteins. The early expression of myopodin prior to sarcomeric α-actinin, as well as its binding to actin, α-actinin and filamin indicate an important role for this protein in actin cytoskeleton remodelling with the precise function of myopodin in this process yet remaining to be resolved. While myopodin was previously described as a protein capable of cross-linking actin filaments into thick bundles upon transient transfections, it has remained unclear whether myopodin alone is capable of bundling actin, or if additional proteins are involved. We have therefore investigated the in vitro actin binding properties of myopodin. High speed cosedimentation assays with skeletal muscle actin confirmed direct binding of myopodin to F-actin and showed that this interaction is mediated by at least two independent actin binding sites, found in all myopodin isoforms identified to date. Furthermore, low-speed cosedimentation assays revealed that not only full length myopodin, but also the fragment containing only the second binding site, bundles microfilaments in the absence of accessory proteins. Ultrastructural analysis demonstrated that this bundling activity resembled that of α-actinin. Biochemical experiments revealed that bundling was not achieved by myopodin’s ability to dimerize, indicating the presence of two individual F-actin binding sites within the second binding segment. Thus full length myopodin contains at least three F-actin binding sites. These data provide further understanding of the mechanisms by which myopodin contributes to actin reorganization during myofibril assembly.Keywords
This publication has 45 references indexed in Scilit:
- Phosphorylation and interaction of myopodin by integrin-link kinase lead to suppression of cell growth and motility in prostate cancer cellsOncogene, 2011
- The sarcomeric Z-disc component myopodin is a multiadapter protein that interacts with filamin and α-actininEuropean Journal of Cell Biology, 2010
- Protein Kinase A, Ca2+/Calmodulin-Dependent Kinase II, and Calcineurin Regulate the Intracellular Trafficking of Myopodin between the Z-Disc and the Nucleus of Cardiac MyocytesMolecular and Cellular Biology, 2007
- Disease-associated mutant α-actinin-4 reveals a mechanism for regulating its F-actin-binding affinityProceedings of the National Academy of Sciences of the United States of America, 2007
- Xin-repeats and Nebulin-like Repeats Bind to F-actin in a Similar MannerJournal of Molecular Biology, 2006
- Promotion of importin α–mediated nuclear import by the phosphorylation-dependent binding of cargo protein to 14-3-3The Journal of cell biology, 2005
- Tumor suppressor role for myopodin in bladder cancer: loss of nuclear expression of myopodin is cell-cycle dependent and predicts clinical outcomeOncogene, 2003
- Myopodin, a Synaptopodin Homologue, Is Frequently Deleted in Invasive Prostate CancersThe American Journal of Pathology, 2001
- CH domains revisitedFEBS Letters, 1998
- How to measure and predict the molar absorption coefficient of a proteinProtein Science, 1995