Identification of the essential protein domains for Mib2 function during the development of the Drosophila larval musculature and adult flight muscles

Abstract

The proper differentiation and maintenance of myofibers is fundamental to a functional musculature. Disruption of numerous mostly structural factors leads to perturbations of these processes. Among the limited number of known regulatory factors for these processes is Mind bomb2 (Mib2), a muscle-associated E3 ubiquitin ligase, which was previously established to be required for maintaining the integrity of larval muscles. In this study, we have examined the mechanistic aspects of Mib2 function by performing a detailed functional dissection of the Mib2 protein. We show that the ankyrin repeats, in its entirety, and the hitherto uncharacterized Mib-specific domains (MIB), are important for the major function of Mib2 in skeletal and visceral muscles in the Drosophila embryo. Furthermore, we characterize novel mib2 alleles that have arisen from a forward genetic screen aimed at identifying regulators of myogenesis. Two of these alleles are viable, but flightless hypomorphic mib2 mutants, and harbor missense mutations in the MIB domain and RING finger, respectively. Functional analysis of these new alleles, including in vivo imaging, demonstrates that Mib2 plays an additional important role in the development of adult thorax muscles, particularly in maintaining the larval templates for the dorsal longitudinal indirect flight muscles during metamorphosis.

Activation of the ubiquitin-proteasome system contributes to oculopharyngeal muscular dystrophy through muscle atrophy

“…The proteasome maturation protein, Pomp coordinates the assembly of the 20S core proteasome complex and is required for production of newly formed proteasome [ 44 – 47 ]. Mind bomb 2 (Mib2) is a E3 ubiquitin ligase specific to muscles whose E3-RING-finger domains are required for myoblast fusion in the embryo, and development of thoracic indirect flight muscles (IFMs) in adult flies [ 48 , 49 ]. In addition, although Mib2 direct targets have not been identified, Mib2 was shown to physically interact with the Z-band-localized nonmuscle myosin [ 48 ].…”

APC/CFzr regulates cardiac and myoblast cell numbers, and plays a crucial role during myoblast fusion

“…The ubiquitin-proteasome pathway in Drosophila myogenesis Although, no in vivo function of the APC/C during muscle development has been reported previously, our study is not the first description of involvement of the ubiquitin-proteasome pathway in Drosophila myogenesis. Mind bomb 2 (Mib2), another E3ubiquitin ligase was shown to be expressed in FCs and to be involved in myoblast fusion, muscle attachment as well as sarcomere stability (Carrasco-Rando and Ruiz-Gómez, 2008;Domsch et al, 2017;Nguyen et al, 2007). Loss of mib2 causes accumulation of the Gli-like transcription factor Lmd, which is expressed in all FCMs and crucial for the correct differentiation of these cells (Duan et al, 2001;Ruiz-Gómez et al, 2002).…”

MuRF‐1 is Involved in Laryngeal Muscle Denervation Atrophy by Regulating G‐Actin Ubiquitination

“…In C2C12 myoblasts, increase of G/F‐actin ratio led to actin remodeling defects, contributing to further defects in myoblast fusion and differentiation 25 . Notably, G‐actin polymerization and F‐actin depolymerization usually rely on the participation of G‐actin, ATP, Profilin, Thymosin‐β4, and Cofilin‐1, which contribute to the highly dynamic actin filaments of the cytoskeleton in myocytes, as shown in Figure 6 7,12,26,27 . These results suggest that the cytoskeletal remodeling of denervated internal laryngeal myocytes was deprived, and consequently myocyte atrophy occurred.…”