The integrin‐adhesome is required to maintain muscle structure, mitochondrial ATP production, and movement forces inCaenorhabditis elegans

Abstract

The integrin-adhesome network, which contains >150 proteins, is mechano-transducing and located at discreet positions along the cell-cell and cell-extracellular matrix interface. A small subset of the integrin-adhesome is known to maintain normal muscle morphology. However, the importance of the entire adhesome for muscle structure and function is unknown. We used RNA interference to knock down 113 putative Caenorhabditis elegans homologs constituting most of the mammalian adhesome and 48 proteins known to localize to attachment sites in C. elegans muscle. In both cases, we found >90% of components were required for normal muscle mitochondrial structure and/or proteostasis vs. empty vector controls. Approximately half of these, mainly proteins that physically interact with each other, were also required for normal sarcomere and/or adhesome structure. Next we confirmed that the dystrophy observed in adhesome mutants associates with impaired maximal mitochondrial ATP production (P < 0.01), as well as reduced probability distribution of muscle movement forces compared with wild-type animals. Our results show that the integrin-adhesome network as a whole is required for maintaining both muscle structure and function and extend the current understanding of the full complexities of the functional adhesome in vivo.—Etheridge, T., Rahman, M., Gaffney, C. J., Shaw, D., Shephard, F., Magudia, J., Solomon, D. E., Milne, T., Blawzdziewicz, J., Constantin-Teodosiu, D., Greenhaff, P. L., Vanapalli, S. A., Szewczyk, N. J. The integrin-adhesome is required to maintain muscle structure, mitochondrial ATP production, and movement forces in Caenorhabditis elegans.

Degenerin channel activation causes caspase-mediated protein degradation and mitochondrial dysfunction in adultC. elegansmuscle

“…JC‐1 Fluorescence‐activated cell sorting (FACS). Animals were cultured and mitochondria isolated as described . Mitochondria were incubated in the dark for 15 min at 37°C in 20 μM glutamate, 2 mM malate, 6 μM JC‐1 (Invitrogen, UK).…”

“…Maximal rates of ATP production (MRAP). Maximal rates of ATP production (MRAP) were assessed as described . Mixed‐stage populations were used to obtain sufficient quantity of mitochondria as unc‐105 mutants are very sick, taking at least 2–3 weeks to produce a population capable of exhausting food supplies on a plate.…”

“…These signals converge, modulating activation of autophagy via mitogen‐activated protein kinase (MAPK), and appear relevant to a model of neurodegeneration and to ageing . Lastly, calpains are activated in response to muscle attachment complex disruption, which appears required to maintain muscle in response to use …”

“…12 Lastly, calpains are activated in response to muscle attachment complex disruption, which appears required to maintain muscle in response to use. 13,14 Recently, unc-105 gain-of-function mutants were reported to display increased muscle protein degradation via an unknown mechanism. 5 unc-105 encodes a putative mechano-sensitive ion channel of the ENaC/degenerin family.…”

Functional phosphatome requirement for protein homeostasis, networked mitochondria, and sarcomere structure in C. elegans muscle

“…Far left (green): caspase activation is induced by mitochondrial dysfunction, which can be caused by loss of degenerin channel contact with collagen in the extracellular matrix 19. Left (violet): degradation by calpains is regulated by integrin attachment to the basement membrane,18 and a significant portion of the integrin adhesome appears to contribute to this regulation 16. Middle (yellow): autophagic degradation is controlled by a balance of signal from insulin/insulin‐like receptor (negative regulator, green lines) and autocrine fibroblast growth factor signal (positive regulator, red lines) 12, 13, 14.…”