The quest for substrates and binding partners: A critical barrier for understanding the role of ADAMTS proteases in musculoskeletal development and disease

Abstract

Secreted ADAMTS metalloproteases are involved in the sculpting, remodeling, and erosion of connective tissues throughout the body, including in the musculoskeletal system. ADAMTS proteases contribute to musculoskeletal development, pathological tissue destruction, and are mutated in congenital musculoskeletal disorders. Examples include versican cleavage by ADAMTS9 which is required for interdigital web regression during limb development, ADAMTS5-mediated aggrecan degradation in osteoarthritis resulting in joint erosion, and mutations in ADAMTS10 or ADAMTS17 that cause Weill-Marchesani syndrome, a short stature syndrome with bone, joint, muscle, cardiac, and eye involvement. Since the function of ADAMTS proteases and proteases in general is primarily defined by the molecular consequences of proteolysis of their respective substrates, it is paramount to identify all physiological substrates for each individual ADAMTS protease. Here, we review the current knowledge of ADAMTS proteases and their involvement in musculoskeletal development and disease, focusing on some of their known physiological substrates and the consequences of substrate cleavage. We further emphasize the critical need for the identification and validation of novel ADAMTS substrates and binding partners by describing the principles of mass spectrometry-based approaches and by emphasizing strategies that need to be considered for validating the physiological relevance for ADAMTS-mediated proteolysis of novel putative substrates.

Alternative splicing of the metalloprotease ADAMTS17 spacer regulates secretion and modulates autoproteolytic activity

“…To elucidate the biological functions of the ADAMTS17 protease, it will be paramount to identify the substrates for ADAMTS17 and determine if they differ between its isoforms. 40 Such efforts are currently underway in the laboratory. In the meantime, we capitalized on the known autoproteolytic activity as a surrogate substrate to test the functional impact of the new ADAMTS17 isoforms.…”

Regulation of ADAMTS Proteases

“…The a disintegrin and metalloprotease with thrombospondin type I motifs (ADAMTS) protease family comprises 19 secreted metalloproteases with a broad substrate and functional spectrum that is ever expanding due to recent advances in mass spectrometry-based substrate identification and due to the characterization of knock-out mouse models for most of the ADAMTS proteases ( Puente et al, 2003 ; Kleifeld et al, 2011 ; Dubail and Apte, 2015 ; Savickas and Auf dem Keller, 2017 ; Apte, 2020 ; Satz-Jacobowitz and Hubmacher, 2021 ). Commensurate with the broad substrate and functional spectrum, ADAMTS proteases play major roles in organ development and tissue homeostasis by regulating extracellular matrix (ECM) formation, remodeling and homeostatic adaptation.…”

“…While it is certainly true that most of the biology of ADAMTS proteases, or any protease for that matter, is ultimately defined by the consequences of substrate cleavage in vivo , it is equally important to elucidate the mechanisms by which ADAMTS protease activity is regulated during tissue development and maturation to fully understand how ADAMTS proteases work ( Jones and Riley, 2005 ; Apte, 2020 ; Satz-Jacobowitz and Hubmacher, 2021 ). By regulating ADAMTS protease activity itself, the fate of entire groups of ECM substrates can be simultaneously altered and therefore, these proteases could be seen akin to nodes in a regulatory network that could be targeted in disorders such as arthritis, where ADAMTS protease activity is pathologically upregulated.…”

“…Several aspects of ADAMTS proteases have been reviewed recently, including structural considerations, evolutionary aspects, the implication of ADAMTS proteases in inherited connective tissue disorders and the importance of substrate identification in understanding ADAMTS protease biology ( Nicholson et al, 2005 ; Brunet et al, 2015 ; Takeda, 2016 ; Mead and Apte, 2018 ; Apte, 2020 ; Satz-Jacobowitz and Hubmacher, 2021 ). Here, we summarize recent insights into the mechanisms that regulate ADAMTS protease activity that could potentially be harnessed to modulate ADAMTS-mediated substrate cleavage, specifically in the context of degenerative connective tissue disorders.…”

Musculoskeletal Development, Maintenance and Regeneration: Part One

“…Regulating both matrix composition/assembly and growth factor signaling pathways is the ADAMTS family of metalloproteinases. In their critical commentary, Satz‐Jacobowitz and Hubmacher 8 review this large protease family covering their protein structure, expression, and roles during development, tissue maintenance, and disease. There is no consensus cleavage site for the ADAMTS metalloproteinase family, and an outstanding question in the field is about their range of physiological substrates, including those for the relatively uncharacterized orphan receptors.…”