Conserved function of the matriptase-prostasin proteolytic cascade during epithelial morphogenesis

Distinct enzyme activities of serine protease p37k in silkworm midgut and molting fluid

Serine proteases possess various biological functions. The serine protease p37k exhibits gelatinolytic activity in the silkworm midgut and degrades cuticular proteins in the molting fluid. In this study, we analyzed the activity changes of recombinant p37k (re-p37k) and p37k in the midgut and molting fluid of Bombyx mori. Firstly, in vitro-expressed re-p37k was activated when a 22 kDa band was observed by western blot. Re-p37k exhibits strong gelatinolytic activity, with the highest activity observed at pH 7.0-9.0 and 45 °C. Compared to p37k in the midgut, re-p37k loses thermal stability but can be restored by midgut extract or ions. E64, AEBSF, and an inhibitor cocktail inhibited the hydrolytic activity of re-p37k on epidermal proteins but did not inhibit the gelatinolytic activity. Subsequently, zymography showed that the positions of gelatinolytic band produced by p37k in the midgut and molting fluid were different, 35 kDa and 40 kDa, respectively. Finally, when heated midgut extract was added to re-p37k or molting fluid, the gelatinolytic band shifted from 40 kDa to 35 kDa, and the proteolytic activity of p37k in the molting fluid was inhibited. Collectively, our results demonstrate that p37k exhibits different activities in various tissues, suggesting its distinct tissue-specific functions during insect metamorphosis.

Apical cell expansion maintained by Dusky-like establishes a scaffold for corneal lens morphogenesis

The biconvex shape of the Drosophila corneal lens, which enables it to focus light onto the retina, arises by organized assembly of chitin and other apical extracellular matrix components. We show here that the Zona Pellucida domain-containing protein Dusky-like is essential for normal corneal lens morphogenesis. Dusky-like transiently localizes to the expanded apical surfaces of the corneal lens-secreting cells, and in its absence, these cells undergo apical constriction and apicobasal contraction. Dusky-like also controls the arrangement of two other Zona Pellucida-domain proteins, Dumpy and Piopio, external to the developing corneal lens. Loss of either dusky-like or dumpy delays chitin accumulation and disrupts the outer surface of the corneal lens. Artificially inducing apical constriction with constitutively active Myosin light chain kinase is sufficient to similarly alter chitin deposition and corneal lens morphology. These results demonstrate the importance of cell shape for the morphogenesis of overlying apical extracellular matrix structures.

A surfactant lipid layer of endosomal membranes facilitates airway gas filling in Drosophila

The mechanisms underlying the construction of an air-liquid interface in respiratory organs remain elusive. Here, we use live imaging and genetic analysis to describe the morphogenetic events generating an extracellular lipid lining of the Drosophila airways required for their gas filing and animal survival. We show that sequential Rab39/Syx1A/Syt1-mediated secretion of lysosomal acid sphingomyelinase (Drosophila ASM [dASM]) and Rab11/35/Syx1A/Rop-dependent exosomal secretion provides distinct components for lipid film assembly. Tracheal inactivation of Rab11 or Rab35 or loss of Rop results in intracellular accumulation of exosomal, multi-vesicular body (MVB)-derived vesicles. On the other hand, loss of dASM or Rab39 causes luminal bubble-like accumulations of exosomal membranes and liquid retention in the airways. Inactivation of the exosomal secretion in dASM mutants counteracts this phenotype, arguing that the exosomal secretion provides the lipid vesicles and that secreted lysosomal dASM organizes them into a continuous film. Our results reveal the coordinated functions of extracellular vesicle and lysosomal secretions in generating a lipid layer crucial for airway gas filling and survival.

The proteolysis of ZP proteins is essential to control cell membrane structure and integrity of developing tracheal tubes in Drosophila

Membrane expansion integrates multiple forces to mediate precise tube growth and network formation. Defects lead to deformations, as found in diseases such as polycystic kidney diseases, aortic aneurysms, stenosis, and tortuosity. We identified a mechanism of sensing and responding to the membrane-driven expansion of tracheal tubes. The apical membrane is anchored to the apical extracellular matrix (aECM) and causes expansion forces that elongate the tracheal tubes. The aECM provides a mechanical tension that balances the resulting expansion forces, with Dumpy being an elastic molecule that modulates the mechanical stress on the matrix during tracheal tube expansion. We show in Drosophila that the zona pellucida (ZP) domain protein Piopio interacts and cooperates with the ZP protein Dumpy at tracheal cells. To resist shear stresses which arise during tube expansion, Piopio undergoes ectodomain shedding by the Matriptase homolog Notopleural, which releases Piopio-Dumpy-mediated linkages between membranes and extracellular matrix. Failure of this process leads to deformations of the apical membrane, tears the apical matrix, and impairs tubular network function. We also show conserved ectodomain shedding of the human TGFβ type III receptor by Notopleural and the human Matriptase, providing novel findings for in-depth analysis of diseases caused by cell and tube shape changes.

Spatiotemporal remodeling of extracellular matrix orients epithelial sheet folding

Biological systems are inherently noisy; however, they produce highly stereotyped tissue morphology. Drosophila pupal wings show a highly stereotypic folding through uniform expansion and subsequent buckling of wing epithelium within a surrounding cuticle sac. The folding pattern produced by buckling is generally stochastic; it is thus unclear how buckling leads to stereotypic tissue folding of the wings. We found that the extracellular matrix (ECM) protein, Dumpy, guides the position and direction of buckling-induced folds. Dumpy anchors the wing epithelium to the overlying cuticle at specific tissue positions. Tissue-wide alterations of Dumpy deposition and degradation yielded different buckling patterns. In summary, we propose that spatiotemporal ECM remodeling shapes stereotyped tissue folding through dynamic interactions between the epithelium and its external structures.

Prognostic Genomic Markers of Pathological Stage in Oral Squamous Cell Carcinoma

BACKGROUND

To identify the prognostic markers of oral squamous cell carcinoma (OSCC), the genetic heterogeneity of the pathological stages was investigated.

METHODS

The data of 295 patients with primary OSCC obtained from the Cancer Genome Atlas were studied. The genetic prognostic landscape of the pathological stages was systematically analyzed by Cox regressions, Fisher's exact tests, and Gene Ontology (GO) enrichment.

RESULTS

Stage 4 patients had a poor prognosis in univariate and multivariate Cox models. Transforming growth factor-beta (TGF-β) pathway alterations were found more frequently in stage 4, whereas alterations in cell cycle pathways were significant in stages 1, 2, and 3. The differentially mutated genes were divided into three groups: risk genes of high stage, hazardless genes, and risk genes of low stage. The risk genes of low stage (RNF112, AKR7L, ZSCAN5C, and ZPBP) were independent prognostic factors with stage 4 and treatment modality in multivariate Cox regressions. Additionally, in genetic interaction analysis, NOMO1 and ZNF333 had a high co-occurrence in high stage, and WIZ had high co-occurrence in low stage. In GO enrichment, the prognostic genes were clustered at the functional term of RNA polymerase II transcription, and ZNF333 had an association with RNA transcription.

CONCLUSION

The genetic mutation type and ratio of tumor heterogeneity are different for each stage of OSCC, and stratification of OSCC patients with differential therapeutic efficacy is needed. Risk genes of both high and low stages must be identified in patients diagnosed with low-stage OSCC. Mutations in NOMO1, ZNF333, and WIZ should be considered as potential prognostic markers.

Multifactorial Traits of SARS-CoV-2 Cell Entry Related to Diverse Host Proteases and Proteins

The most effective way to control newly emerging infectious disease, such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, is to strengthen preventative or therapeutic public health strategies before the infection spreads worldwide. However, global health systems remain at the early stages in anticipating effective therapeutics or vaccines to combat the SARS-CoV-2 pandemic. While maintaining social distance is the most crucial metric to avoid spreading the virus, symptomatic therapy given to patients on the clinical manifestations helps save lives. The molecular properties of SARS-CoV-2 infection have been quickly elucidated, paving the way to therapeutics, vaccine development, and other medical interventions. Despite this progress, the detailed biomolecular mechanism of SARS-CoV-2 infection remains elusive. Given virus invasion of cells is a determining factor for virulence, understanding the viral entry process can be a mainstay in controlling newly emerged viruses. Since viral entry is mediated by selective cellular proteases or proteins associated with receptors, identification and functional analysis of these proteins could provide a way to disrupt virus propagation. This review comprehensively discusses cellular machinery necessary for SARS-CoV-2 infection. Understanding multifactorial traits of the virus entry will provide a substantial guide to facilitate antiviral drug development.

Form and function of the apical extracellular matrix: new insights from Caenorhabditis elegans, Drosophila melanogaster, and the vertebrate inner ear

Apical extracellular matrices (aECMs) are the extracellular layers on the apical sides of epithelia. aECMs form the outer layer of the skin in most animals and line the luminal surface of internal tubular epithelia. Compared to the more conserved basal ECMs (basement membranes), aECMs are highly diverse between tissues and between organisms and have been more challenging to understand at mechanistic levels. Studies in several genetic model organisms are revealing new insights into aECM composition, biogenesis, and function and have begun to illuminate common principles and themes of aECM organization. There is emerging evidence that, in addition to mechanical or structural roles, aECMs can participate in reciprocal signaling with associated epithelia and other cell types. Studies are also revealing mechanisms underlying the intricate nanopatterns exhibited by many aECMs. In this review, we highlight recent findings from well-studied model systems, including the external cuticle and ductal aECMs of Caenorhabditis elegans, Drosophila melanogaster, and other insects and the internal aECMs of the vertebrate inner ear.

Priming of SARS-CoV-2 S protein by several membrane-bound serine proteinases could explain enhanced viral infectivity and systemic COVID-19 infection

The ongoing COVID-19 pandemic has already caused over a million deaths worldwide, and this death toll will be much higher before effective treatments and vaccines are available. The causative agent of the disease, the coronavirus SARS-CoV-2, shows important similarities with the previously emerged SARS-CoV-1, but also striking differences. First, SARS-CoV-2 possesses a significantly higher transmission rate and infectivity than SARS-CoV-1 and has infected in a few months over 60 million people. Moreover, COVID-19 has a systemic character, as in addition to the lungs, it also affects the heart, liver, and kidneys among other organs of the patients and causes frequent thrombotic and neurological complications. In fact, the term "viral sepsis" has been recently coined to describe the clinical observations. Here I review current structure-function information on the viral spike proteins and the membrane fusion process to provide plausible explanations for these observations. I hypothesize that several membrane-associated serine proteinases (MASPs), in synergy with or in place of TMPRSS2, contribute to activate the SARS-CoV-2 spike protein. Relative concentrations of the attachment receptor, ACE2, MASPs, their endogenous inhibitors (the Kunitz-type transmembrane inhibitors, HAI-1/SPINT1 and HAI-2/SPINT2, as well as major circulating serpins) would determine the infection rate of host cells. The exclusive or predominant expression of major MASPs in specific human organs suggests a direct role of these proteinases in e.g., heart infection and myocardial injury, liver dysfunction, kidney damage, as well as neurological complications. Thorough consideration of these factors could have a positive impact on the control of the current COVID-19 pandemic.

Glycosylhydrolase genes control respiratory tubes sizes and airway stability

Tight barriers are crucial for animals. Insect respiratory cells establish barriers through their extracellular matrices. These chitinous-matrices must be soft and flexible to provide ventilation, but also tight enough to allow oxygen flow and protection against dehydration, infections, and environmental stresses. However, genes that control soft, flexible chitin-matrices are poorly known. We investigated the genes of the chitinolytic glycosylhydrolase-family 18 in the tracheal system of Drosophila melanogaster. Our findings show that five chitinases and three chitinase-like genes organize the tracheal chitin-cuticles. Most of the chitinases degrade chitin from airway lumina to enable oxygen delivery. They further improve chitin-cuticles to enhance tube stability and integrity against stresses. Unexpectedly, some chitinases also support chitin assembly to expand the tube lumen properly. Moreover, Chitinase2 plays a decisive role in the chitin-cuticle formation that establishes taenidial folds to support tube stability. Chitinase2 is apically enriched on the surface of tracheal cells, where it controls the chitin-matrix architecture independently of other known cuticular proteins or chitinases. We suppose that the principle mechanisms of chitin-cuticle assembly and degradation require a set of critical glycosylhydrolases for flexible and not-flexible cuticles. The same glycosylhydrolases support thick laminar cuticle formation and are evolutionarily conserved among arthropods.

Membrane-anchored serine proteases as regulators of epithelial function

Cleavage of proteins in the extracellular milieu, including hormones, growth factors and their receptors, ion channels, and various cell adhesion and extracellular matrix molecules, plays a key role in the regulation of cell behavior. Among more than 500 proteolytic enzymes encoded by mammalian genomes, membrane-anchored serine proteases (MASPs), which are expressed on the surface of epithelial cells of all major organs, are excellently suited to mediate signal transduction across the epithelia and are increasingly being recognized as important regulators of epithelial development, function, and disease [ 1-3]. In this minireview, we summarize current knowledge of the in vivo roles of MASPs in acquisition and maintenance of some of the defining functions of epithelial tissues, such as barrier formation, ion transport, and sensory perception.

Control of tissue morphogenesis by the HOX gene Ultrabithorax

Mutations in the Ultrabithorax (Ubx) gene cause homeotic transformation of the normally two-winged Drosophila into a four-winged mutant fly. Ubx encodes a HOX family transcription factor that specifies segment identity, including transformation of the second set of wings into rudimentary halteres. Ubx is known to control the expression of many genes that regulate tissue growth and patterning, but how it regulates tissue morphogenesis to reshape the wing into a haltere is still unclear. Here, we show that Ubx acts by repressing the expression of two genes in the haltere, Stubble and Notopleural, both of which encode transmembrane proteases that remodel the apical extracellular matrix to promote wing morphogenesis. In addition, Ubx induces expression of the Tissue inhibitor of metalloproteases in the haltere, which prevents the basal extracellular matrix remodelling necessary for wing morphogenesis. Our results provide a long-awaited explanation for how Ubx controls morphogenetic transformation.