A Common Suite of Coagulation Proteins Function inDrosophilaMuscle Attachment

Abstract

The organization and stability of higher order structures that form in the extracellular matrix (ECM) to mediate the attachment of muscles are poorly understood. We have made the surprising discovery that a subset of clotting factor proteins are also essential for muscle attachment in the model organism Drosophila melanogaster One such coagulation protein, Fondue (Fon), was identified as a novel muscle mutant in a pupal lethal genetic screen. Fon accumulates at muscle attachment sites and removal of this protein results in decreased locomotor behavior and detached larval muscles. A sensitized genetic background assay reveals that fon functions with the known muscle attachment genes Thrombospondin (Tsp) and Tiggrin (Tig). Interestingly, Tig is also a component of the hemolymph clot. We further demonstrate that an additional clotting protein, Larval serum protein 1γ (Lsp1γ), is also required for muscle attachment stability and accumulates where muscles attach to tendons. While the local biomechanical and organizational properties of the ECM vary greatly depending on the tissue microenvironment, we propose that shared extracellular protein-protein interactions influence the strength and elasticity of ECM proteins in both coagulation and muscle attachment.

Proteomics of protein trafficking byin vivotissue-specific labeling

“…2G; details and references in Table S2). For instance, the FB-secreted fon has been previously detected in muscles and Droujinine et al 7 shown to regulate their functions (14). Moreover, we identified additional secreted proteins previously unknown to be produced by FB or to traffic to legs or muscles ( Fig.…”

A tissue communication network coordinating innate immune response during muscle stress

“…These experiments establish muscle as a key immuneresponsive tissue in the defense against infection in both invertebrates and vertebrates. Further supporting a shared connection between muscle maintenance and innate immunity, we recently identified fondue (fon) as essential for maintaining the extracellular matrix (ECM) of the larval muscle attachment site (MAS) (Green et al, 2016). The common suite of secreted hemolymph proteins that accumulate and function at the MAS were also found to act with Fon in its previously described role in coagulation (Bajzek et al, 2012;Lindgren et al, 2008;Scherfer et al, 2006).…”

“…Our results thus far show that knockdown of two genes required for muscle attachment (Tig and stck) activate local JAK-STAT signaling in muscle. We previously identified Fon as a novel ECM organizer in preserving larval MASs (Green et al, 2016). Owing to its strong detachment phenotype and the ability to bypass the embryonic lethality that complicates the analysis of similar mutants (i.e.…”

“…We first tested the effects of knocking down cactus (cact), as elongated pupal phenotypes present in cact mutants are similar to those observed in fon mutants (Green et al, 2016;Letsou et al, 1991). The NF-κB inhibitor, cact, is responsible for sequestering the transcription factors, Dif and Dl, in the cytoplasm until Toll signal transduction proceeds.…”

“…Here, we have uncovered a tissue communication network linking muscle maintenance and innate immune signaling. While characterizing the muscle phenotypes of fon mutants (Green et al, 2016), we noted several immune responses resulting from damaged muscle tissue, including the deposition of melanin at MASs, hemocyte recruitment to detached and torn muscles, and the activation of both JAK-STAT and Toll signaling. Importantly, we also show that JAK-STAT and Toll have the ability to establish a reciprocal signaling network between tissues that sense and respond to cellular stress.…”