title: Ankyrin-B interactions with spectrin and dynactin-4 are required for dystrophin-based protection of skeletal muscle from exercise injury.
abstract: Costameres are cellular sites of mechanotransduction in heart and skeletal muscle where dystrophin and its membrane-spanning partner dystroglycan distribute intracellular contractile forces into the surrounding extracellular matrix. Resolution of a functional costamere interactome is still limited but likely to be critical for understanding forms of muscular dystrophy and cardiomyopathy. Dystrophin binds a set of membrane-associated proteins (the dystrophin-glycoprotein complex) as well as γ-actin and microtubules and also is required to align sarcolemmal microtubules with costameres. Ankyrin-B binds to dystrophin, dynactin-4, and microtubules and is required for sarcolemmal association of these proteins as well as dystroglycan. We report here that ankyrin-B interactions with β2 spectrin and dynactin-4 are required for localization of dystrophin, dystroglycan, and microtubules at costameres as well as protection of muscle from exercise-induced injury. Knockdown of dynactin-4 in adult mouse skeletal muscle phenocopied depletion of ankyrin-B and resulted in loss of sarcolemmal dystrophin, dystroglycan, and microtubules. Moreover, mutations of ankyrin-B and of dynactin-4 that selectively impaired binary interactions between these proteins resulted in loss of their costamere-localizing activity and increased muscle fiber fragility as a result of loss of costamere-associated dystrophin and dystroglycan. In addition, costamere-association of dynactin-4 did not require dystrophin but did depend on β2 spectrin and ankyrin-B, whereas costamere association of ankyrin-B required β2 spectrin. Together, these results are consistent with a functional hierarchy beginning with β2 spectrin recruitment of ankyrin-B to costameres. Ankyrin-B then interacts with dynactin-4 and dystrophin, whereas dynactin-4 collaborates with dystrophin in coordinating costamere-aligned microtubules.
authors.affiliation: Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Gai
authors.initials: G
authors.lastname: Ayalon
authors.forename: Janell D
authors.initials: JD
authors.lastname: Hostettler
authors.forename: Jan
authors.initials: J
authors.lastname: Hoffman
authors.forename: Krishnakumar
authors.initials: K
authors.lastname: Kizhatil
authors.forename: Jonathan Q
authors.initials: JQ
authors.lastname: Davis
authors.forename: Vann
authors.initials: V
authors.lastname: Bennett
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D054974:Costameres / Q000378:metabolism; D000072159:Dynactin Complex; D016189:Dystrophin / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D055785:Gene Knockdown Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D018482:Muscle, Skeletal / Q000293:injuries / Q000378:metabolism / Q000473:pathology; D005082:Physical Exertion / Q000502:physiology; D014947:Wounds and Injuries / Q000378:metabolism / Q000473:pathology; D013049:Spectrin
chemical_list: D017487:Ankyrins; D002352:Carrier Proteins; D000072159:Dynactin Complex; D016189:Dystrophin; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D013049:Spectrin; C498995:Ank2 protein, mouse