Identification of novel MYO18A interaction partners required for myoblast adhesion and muscle integrity

Abstract

The unconventional myosin MYO18A that contains a PDZ domain is required for muscle integrity during zebrafish development. However, the mechanism by which it functions in myofibers is not clear. The presence of a PDZ domain suggests that MYO18A may interact with other partners to perform muscle-specific functions. Here we performed double-hybrid screening and co-immunoprecipitation to identify MYO18A-interacting proteins, and have identified p190RhoGEF and Golgin45 as novel partners for the MYO18A PDZ domain. We have also identified Lurap1, which was previously shown to bind MYO18A. Functional analyses indicate that, similarly as myo18a, knockdown of lurap1, p190RhoGEF and Golgin45 by morpholino oligonucleotides disrupts dystrophin localization at the sarcolemma and produces muscle lesions. Simultaneous knockdown of myo18a with either of these genes severely disrupts myofiber integrity and dystrophin localization, suggesting that they may function similarly to maintain myofiber integrity. We further show that MYO18A and its interaction partners are required for adhesion of myoblasts to extracellular matrix, and for the formation of the Golgi apparatus and organization of F-actin bundles in myoblast cells. These findings suggest that MYO18A has the potential to form a multiprotein complex that links the Golgi apparatus to F-actin, which regulates muscle integrity and function during early development.

Leucine repeat adaptor protein 1 interacts with Dishevelled to regulate gastrulation cell movements in zebrafish

“…These imply that Lurap1 regulates microtubule cytoskeleton organisation in a similar manner as Wnt/PCP signalling. However, we could not at present exclude the possibility that Lurap1 regulates cell polarity independently of Dvl since it also interacts with other proteins such as MRCK and MYO18A that play a role in cell adhesion and migration 40 , 41 . In addition, it is well established that Wnt/PCP signal is transduced via Dvl to the small GTPases Rac and Rho, which activate distinct downstream effectors to modulate the actin cytoskeleton 33 .…”

“…Lurap1 (leucine repeat adaptor protein 1), also known as Lrap35a, is an adaptor protein with two leucine-rich repeats at its N-terminal region and a PDZ-binding motif at the extreme C-terminus 40 . In cultured cells, it has been shown that Lurap1 regulates actomyosin retrograde flow and cell migration by forming a tripartite complex with myotonic dystrophy kinase-related Rac/Cdc42-binding kinase (MRCK), and the unconventional MYO18A through the leucine-rich repeats and the PDZ-binding motif, respectively 40 , 41 . Although this protein is highly conserved among vertebrate species, its implication in regulating cell movements during early development has never been reported.…”

Multifaceted Function of Myosin-18, an Unconventional Class of the Myosin Superfamily

“…Because it is the only myosin-18 in Drosophila , this observation did not provide a clear clue whether myosin-18A is functioning in muscle in vertebrates. There were two consecutive studies in zebrafish that revealed the role of myosin-18A in striated muscle development and function ( Cao et al, 2014 , 2016 ). Two myosin-18A genes MYO18Aα and MYO18Aβ exist in zebrafish, and both of them were expressed in somites during muscle development, and knockdown of MYO18A , as well as overexpression of the PDZ domain disrupted myofiber integrity ( Cao et al, 2014 ).…”

MYO18A: An unusual myosin

“…In zebrafish, gene duplication gave rise to two MYO18A genes, myo18aa and myo18ab. In a pair of publications, Cao et al have studied the function of the two MYO18A genes in zebrafish (Cao et al, 2014, 2016). Using in situ hybridization they detected ubiquitous expression of both genes, with enrichment in the somites.…”