Creatine kinase B is necessary to limit myoblast fusion during myogenesis

Abstract

GK.Creatine kinase B is necessary to limit myoblast fusion during myogenesis. Am J Physiol Cell Physiol 308: C919 -C931, 2015. First published March 25, 2015 doi:10.1152/ajpcell.00029.2015.-Myoblast fusion is critical for proper muscle growth and regeneration. During myoblast fusion, the localization of some molecules is spatially restricted; however, the exact reason for such localization is unknown. Creatine kinase B (CKB), which replenishes local ATP pools, localizes near the ends of cultured primary mouse myotubes. To gain insights into the function of CKB, we performed a yeast two-hybrid screen to identify CKB-interacting proteins. We identified molecules with a broad diversity of roles, including actin polymerization, intracellular protein trafficking, and alternative splicing, as well as sarcomeric components. In-depth studies of ␣-skeletal actin and ␣-cardiac actin, two predominant muscle actin isoforms, demonstrated their biochemical interaction and partial colocalization with CKB near the ends of myotubes in vitro. In contrast to other cell types, specific knockdown of CKB did not grossly affect actin polymerization in myotubes, suggesting other muscle-specific roles for CKB. Interestingly, knockdown of CKB resulted in significantly increased myoblast fusion and myotube size in vitro, whereas knockdown of creatine kinase M had no effect on these myogenic parameters. Our results suggest that localized CKB plays a key role in myotube formation by limiting myoblast fusion during myogenesis.

Srf controls satellite cell fusion through the maintenance of actin architecture

“…In other words, fusion can take place between a control cell and a Srf mutant cell if its F-actin content and the organization of actin into cables are recovered. The possible underlying mechanism for this rescue could be restoration of the mechanical invading force that helps to overcome energy barriers for membrane apposition and drives cell membrane fusion ( Kim et al, 2015b ) or the appropriate cellular distribution of signaling molecules or contractile protein molecules required for fusion ( Tran et al, 2012 ; Simionescu-Bankston et al, 2015 ).…”

Cellular compartmentation of energy metabolism: creatine kinase microcompartments and recruitment of B-type creatine kinase to specific subcellular sites

“…Interaction databases list microtubule-interacting protein associated with TRAF3 (MIP-T3) as a BCK-interacting cystoskeletal protein of unknown function (Guo et al 2010), which may be a candidate for cytoskeletal BCK receptors such as the one involved in recruitment to F-actin. In cultured mouse myotubes, where BCK localizes near the endings of the cells, Y2H and other assays suggest an interaction with skeletal and cardiac α-actin (Simionescu-Bankston et al 2015). However, this BCK seems not to be involved in actin polymerization, but rather in myotube formation by limiting myoblast fusion during myogenesis.…”

Altered in vitro muscle differentiation in X-linked myopathy with excessive autophagy (XMEA)

“…In this sense, in a recent study analyzing a model of myoblasts with a decline in fusion capacity, the authors also observed no alteration in the expression of myogenic factors such as Myog, highlighting the possibility of morphological alterations without changes in the myogenic program (Park et al, 2016). Previous studies have also found enhanced fusion in myoblasts upon genetic modulation of factors such as insulin-like growth factor-1 (IGF-1) (Jacquemin et al, 2007), mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) , matrix metallopeptidase 7 (MMP-7) (Caron et al, 1999), creatine kinase b (CKB) (Simionescu-Bankston et al, 2015) or stabilin-2 (Stab-2) (Park et al, 2016), emphasizing the number of distinct cellular pathways that, when altered, may lead to enhanced myotube formation. Upon treating cells with chloroquine, we did not observe changes in myoblast fusion, indicating that lysosomal acidification is not the major player regulating this process.…”