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

Secreted ADAMTS-like proteins as regulators of connective tissue function

The extracellular matrix (ECM) determines functional properties of connective tissues through structural components, such as collagens, elastic fibers, or proteoglycans. The ECM also instructs cell behavior through regulatory proteins, including proteases, growth factors, and matricellular proteins, which can be soluble or tethered to ECM scaffolds. The secreted a disintegrin and metalloproteinase with thrombospondin type 1 repeats/motifs-like (ADAMTSL) proteins constitute a family of regulatory ECM proteins that are related to ADAMTS proteases but lack their protease domains. In mammals, the ADAMTSL protein family comprises seven members, ADAMTSL1-6 and papilin. ADAMTSL orthologs are also present in the worm, Caenorhabditis elegans, and the fruit fly, Drosophila melanogaster. Like other matricellular proteins, ADAMTSL expression is characterized by tight spatiotemporal regulation during embryonic development and early postnatal growth and by cell type- and tissue-specific functional pleiotropy. Although largely quiescent during adult tissue homeostasis, reexpression of ADAMTSL proteins is frequently observed in the context of physiological and pathological tissue remodeling and during regeneration and repair after injury. The diverse functions of ADAMTSL proteins are further evident from disorders caused by mutations in individual ADAMTSL proteins, which can affect multiple organ systems. In addition, genome-wide association studies (GWAS) have linked single nucleotide polymorphisms (SNPs) in ADAMTSL genes to complex traits, such as lung function, asthma, height, body mass, fibrosis, or schizophrenia. In this review, we summarize the current knowledge about individual members of the ADAMTSL protein family and highlight recent mechanistic studies that began to elucidate their diverse functions.

Abnormal lens thickening in a child with Weill-Marchesani syndrome 4: A 3-year follow-up case report

Background

Weill-Marchesani syndrome 4 (WMS4) is caused by ADAMTS17 gene variant and clinical abnormalities including lenticular myopia, ectopia lentis, glaucoma, microspherophakia, brachydactyly, and short stature. Due to free of heart defects and joint stiffness compared with other WMS forms, WMS4 has an insidious onset and is often misdiagnosed as high myopia. We combined multiple imaging biometry and whole-exome sequencing to diagnose a case of WMS4 with a 3-year follow-up.

Case presentation

An 8-year-old boy presented to our ophthalmology department with progressive myopia for 1 year. He had high myopia in both eyes with normal funds, intraocular pressure, and axial length. Ocular examination revealed thicker lenses (right 4.38 mm, left 4.31 mm) with a smaller equatorial diameter (right 7.33 mm and left 7.17 mm) compared to normal children of the same age. Finger length measurement indicates brachydactyly. Whole-exome sequencing identified compound heterozygous missense variants c.2984G > A (p.Arg995Gln) and c.2254A > G (p.Ile752Val) in the ADAMTS17 gene. During the 3 years of follow-up, the thickness of lenses increased significantly (right 4.49 mm, left 4.48 mm), but the equatorial diameter of the lenses had no significant change (right 7.32 mm, left 7.21 mm). As the equivalent lens power increased, the patient's myopia spherical refractive error rose accordingly. Although the anterior chamber angle remained open during follow-up, the intraocular pressure increased to right 20.4 mmHg and left 19.6 mmHg, Iridodonesis and short stature were present.

Conclusion

This case report highlights the abnormal thickening of the lens in WMS4 compared to the physiological thinning process during childhood. Comprehensive clinical examinations and genetic testing may improve diagnosis, which allows early therapeutic interventions for complications and better visual outcomes for the patient.

Adamalysins in COVID-19 - Potential mechanisms behind exacerbating the disease

The coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, is a current pandemic that has resulted in nearly 250 million cases and over 5 million deaths. While vaccines have been developed to prevent infection, and most COVID-19 cases end up being fairly light, there are severe cases of COVID-19 that may end up in death, even with adequate healthcare treatment. New options to combat this disease's effects, therefore, could prove to be invaluable in saving lives. Adamalysins are proteins that have several roles in regulating different functions in the human body but are also known to have functions in inflammation. They are also known to have roles in several different diseases, including COVID-19, where ADAM17, in particular, is now well-known to have a prominent role, but also several diseases which include comorbidities that may worsen cases of COVID-19. Therefore, investigating the functions of adamalysins in disease may give us clues to the molecular workings of COVID-19 as well as potentially new therapeutic targets. Understanding these molecular mechanisms may also allow for an understanding of the mechanisms behind the rare severe side effects that occur in response to current COVID-19 vaccines, which may lead to better monitoring measures for people who may be more at risk of developing these side effects. This review investigates the known roles and functions of adamalysins in disease, including what is currently known of their involvement in COVID-19, and how these functions might be involved.

Cooperative Mechanism of ADAMTS/ ADAMTSL and Fibrillin-1 in the Marfan Syndrome and Acromelic Dysplasias

The term “fibrillinopathies” gathers various diseases with a wide spectrum of clinical features and severity but all share mutations in the fibrillin genes. The first described fibrillinopathy, Marfan syndrome (MFS), is a multisystem disease with a unique combination of skeletal, thoracic aortic aneurysm (TAA) and ocular features. The numerous FBN1 mutations identified in MFS are located all along the gene, leading to the same pathogenic mechanism. The geleophysic/acromicric dysplasias (GD/AD), characterized by short stature, short extremities, and joint limitation are described as “the mirror image” of MFS. Previously, in GD/AD patients, we identified heterozygous FBN1 mutations all affecting TGFβ-binding protein-like domain 5 (TB5). ADAMTS10, ADAMTS17 and, ADAMTSL2 are also involved in the pathogenic mechanism of acromelic dysplasia. More recently, in TAA patients, we identified mutations in THSD4, encoding ADAMTSL6, a protein belonging to the ADAMTSL family suggesting that ADAMTSL proteins are also involved in the Marfanoid spectrum. Together with human genetic data and generated knockout mouse models targeting the involved genes, we provide herein an overview of the role of fibrillin-1 in opposite phenotypes. Finally, we will decipher the potential biological cooperation of ADAMTS-fibrillin-1 involved in these opposite phenotypes.

Regulation of ADAMTS Proteases

A disintegrin and metalloprotease with thrombospondin type I motifs (ADAMTS) proteases are secreted metalloproteinases that play key roles in the formation, homeostasis and remodeling of the extracellular matrix (ECM). The substrate spectrum of ADAMTS proteases can range from individual ECM proteins to entire families of ECM proteins, such as the hyalectans. ADAMTS-mediated substrate cleavage is required for the formation, remodeling and physiological adaptation of the ECM to the needs of individual tissues and organ systems. However, ADAMTS proteases can also be involved in the destruction of tissues, resulting in pathologies such as arthritis. Specifically, ADAMTS4 and ADAMTS5 contribute to irreparable cartilage erosion by degrading aggrecan, which is a major constituent of cartilage. Arthritic joint damage is a major contributor to musculoskeletal morbidity and the most frequent clinical indication for total joint arthroplasty. Due to the high sequence homology of ADAMTS proteases in their catalytically active site, it remains a formidable challenge to design ADAMTS isotype-specific inhibitors that selectively inhibit ADAMTS proteases responsible for tissue destruction without affecting the beneficial functions of other ADAMTS proteases. In vivo, proteolytic activity of ADAMTS proteases is regulated on the transcriptional and posttranslational level. Here, we review the current knowledge of mechanisms that regulate ADAMTS protease activity in tissues including factors that induce ADAMTS gene expression, consequences of posttranslational modifications such as furin processing, the role of endogenous inhibitors and pharmacological approaches to limit ADAMTS protease activity in tissues, which almost exclusively focus on inhibiting the aggrecanase activity of ADAMTS4 and ADAMTS5.