Membrane-anchored serine proteases as regulators of epithelial function

Host-derived protease promotes aggregation of Staphylococcus aureus by cleaving the surface protein SasG

Staphylococcus aureus is one of the leading causes of hospital-acquired infections, many of which begin following attachment and accumulation on indwelling medical devices or diseased tissue. These infections are often linked to the establishment of biofilms, but another often overlooked key characteristic allowing S. aureus to establish persistent infection is the formation of planktonic aggregates. Such aggregates are physiologically similar to biofilms and protect pathogens from innate immune clearance and increase antibiotic tolerance. The cell-wall-associated protein SasG has been implicated in biofilm formation via mechanisms of intercellular aggregation but the mechanism in the context of disease is largely unknown. We have previously shown that the expression of cell-wall-anchored proteins involved in biofilm formation is controlled by the ArlRS-MgrA regulatory cascade. In this work, we demonstrate that the ArlRS two-component system controls aggregation, by repressing the expression of sasG by activation of the global regulator MgrA. We also demonstrate that SasG must be proteolytically processed by a non-staphylococcal protease to induce aggregation and that strains expressing functional full-length sasG aggregate significantly upon proteolysis by a mucosal-derived host protease found in human saliva. We used fractionation and N-terminal sequencing to demonstrate that human trypsin within saliva cleaves within the A domain of SasG to expose the B domain and induce aggregation. Finally, we demonstrated that SasG is involved in virulence during mouse lung infection. Together, our data point to SasG, its processing by host proteases, and SasG-driven aggregation as important elements of S. aureus adaptation to the host environment.IMPORTANCEHere, we demonstrate that the Staphylococcus aureus surface protein SasG is important for cell-cell aggregation in the presence of host proteases. We show that the ArlRS two-component regulatory system controls SasG levels through the cytoplasmic regulator MgrA. We identified human trypsin as the dominant protease triggering SasG-dependent aggregation and demonstrated that SasG is important for S. aureus lung infection. The discovery that host proteases can induce S. aureus aggregation contributes to our understanding of how this pathogen establishes persistent infections. The observations in this study demonstrate the need to strengthen our knowledge of S. aureus surface adhesin function and processing, regulation of adhesin expression, and the mechanisms that promote biofilm formation to develop strategies for preventing chronic infections.

ST14 interacts with TMEFF1 and is a predictor of poor prognosis in ovarian cancer

TMEFF1 is a new protein involved in the physiological functions of the central nervous system, and we previously reported TMEFF1 can promote ovarian cancer. ST14 was determined to be involved in the processes of epidermal differentiation, epithelial cell integrity, and vascular endothelial cell migration, etc. The relationship between ST14 and TMEFF1 in the ovary remains unknown. In this study, we detected the expression of ST14 and TMEFF1 in 130 different ovarian cancer tissues through immunohistochemistry. We determined ST14 and TMEFF1 were highly expressed in ovarian cancer, indicating a higher degree of tumor malignancy and a worse prognosis. Tissues significantly expressing ST14 also highly expressed TMEFF1, and the expression of the two proteins was positively correlated. Consistently, immunofluorescence double staining demonstrated the co-localization of ST14 and TMEFF1 in the same region, and immunoprecipitation confirmed the interaction between ST14 and TMEFF1. TMEFF1 expression was also reduced after knocking down ST14 through Western blot. MTT, wound healing and Transwell assays results determined that knockdown of ST14 inhibited proliferation, migration and invasion of ovarian cancer cells in vitro, but the inhibitory effect was restored after adding TMEFF1 exogenous protein. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways analysis showed that ST14 and its related genes were enriched in the processes of epithelial formation, intercellular adhesion, protein localization, and mitosis regulation. We also clarified the kinase, microRNA, and transcription factor target networks and the impact of genetic mutations on prognosis. Overall, high expression of ST14 and TMEFF1 in ovarian cancer predicts higher tumor malignancy and a worse prognosis. ST14 and TMEFF1 co-localize and interact with each other in ovarian cancer. ST14 can regulate TMEFF1 expression to promote proliferation, migration and invasion of ovarian cancer cells. We speculate that the relationship between ST14 and TMEFF1 in ovarian cancer could become a potential target for anti-cancer therapy.

Spatial position is a key determinant of N-glycan functionality of the scavenger receptor cysteine-rich domain of human hepsin

The scavenger receptor cysteine-rich (SRCR) domain is a key constituent in diverse proteins. N-glycosylation is important in protein expression and function. In the SRCR domain of different proteins, N-glycosylation sites and functionality vary substantially. In this study, we examined the importance of N-glycosylation site positions in the SRCR domain of hepsin, a type II transmembrane serine protease involved in many pathophysiological processes. We analysed hepsin mutants with alternative N-glycosylation sites in the SRCR and protease domains using three-dimensional modelling, site-directed mutagenesis, HepG2 cell expression, immunostaining, and western blotting. We found that the N-glycan function in the SRCR domain in promoting hepsin expression and activation on the cell surface cannot be replaced by alternatively created N-glycans in the protease domain. Within the SRCR domain, the presence of an N-glycan in a confined surface area was essential for calnexin-assisted protein folding, endoplasmic reticulum (ER) exiting, and zymogen activation of hepsin on the cell surface. Hepsin mutants with alternative N-glycosylation sites on the opposite side of the SRCR domain were trapped by ER chaperones, resulting in the activation of the unfolded protein response in HepG2 cells. These results indicate that the spatial N-glycan positioning in the SRCR domain is a key determinant in the interaction with calnexin and subsequent cell surface expression of hepsin. These findings may help to understand the conservation and functionality of N-glycosylation sites in the SRCR domains of different proteins.

Corin Deficiency Diminishes Intestinal Sodium Excretion in Mice

Sodium excretion, a critical process in sodium homeostasis, occurs in many tissues, including the kidney and intestine. Unlike in the kidney, the hormonal regulation of intestinal sodium excretion remains unclear. Atrial natriuretic peptide (ANP) is a crucial hormone in renal natriuresis. Corin is a protease critical for ANP activation. Corin and ANP are expressed mainly in the heart. In this study, we investigated corin, ANP, and natriuretic peptide receptor A (Npra) expression in mouse intestines. Corin and ANP expression was co-localized in enteroendocrine cells, whereas Npra expression was on the luminal epithelial cells. In Corin knockout (KO) mice, fecal Na⁺ and Cl^- excretion decreased compared with that in wild-type (WT) mice. Such a decrease was not found in conditional Corin KO mice lacking cardiac corin selectively. In kidney conditional Corin KO mice lacking renal corin, fecal Na⁺ and Cl^- excretion increased, compared to that in WT mice. When WT, Corin KO, and the kidney conditional KO mice were treated with aldosterone, the differences in fecal Na⁺ and Cl^- levels disappeared. These results suggest that intestinal corin may promote fecal sodium excretion in a paracrine mechanism independent of the cardiac corin function. The increased fecal sodium excretion in the kidney conditional Corin KO mice likely reflected an intestinal compensatory response to renal corin deficiency. Our results also suggest that intestinal corin activity may antagonize aldosterone action in the promotion of fecal sodium excretion. These findings help us understand the hormonal mechanism controlling sodium excretion the intestinal tract.

Type II Transmembrane Serine Proteases as Modulators in Adipose Tissue Phenotype and Function

Adipose tissue is a crucial organ in energy metabolism and thermoregulation. Adipose tissue phenotype is controlled by various signaling mechanisms under pathophysiological conditions. Type II transmembrane serine proteases (TTSPs) are a group of trypsin-like enzymes anchoring on the cell surface. These proteases act in diverse tissues to regulate physiological processes, such as food digestion, salt-water balance, iron metabolism, epithelial integrity, and auditory nerve development. More recently, several members of the TTSP family, namely, hepsin, matriptase-2, and corin, have been shown to play a role in regulating lipid metabolism, adipose tissue phenotype, and thermogenesis, via direct growth factor activation or indirect hormonal mechanisms. In mice, hepsin deficiency increases adipose browning and protects from high-fat diet-induced hyperglycemia, hyperlipidemia, and obesity. Similarly, matriptase-2 deficiency increases fat lipolysis and reduces obesity and hepatic steatosis in high-fat diet-fed mice. In contrast, corin deficiency increases white adipose weights and cell sizes, suppresses adipocyte browning and thermogenic responses, and causes cold intolerance in mice. These findings highlight an important role of TTSPs in modifying cellular phenotype and function in adipose tissue. In this review, we provide a brief description about TTSPs and discuss recent findings regarding the role of hepsin, matriptase-2, and corin in regulating adipose tissue phenotype, energy metabolism, and thermogenic responses.

Intersection of Coagulation and Fibrinolysis by the Glycosylphosphatidylinositol (GPI)-Anchored Serine Protease Testisin

Hemostasis is a delicate balance between coagulation and fibrinolysis that regulates the formation and removal of fibrin, respectively. Positive and negative feedback loops and crosstalk between coagulation and fibrinolytic serine proteases maintain the hemostatic balance to prevent both excessive bleeding and thrombosis. Here, we identify a novel role for the glycosylphosphatidylinositol (GPI)-anchored serine protease testisin in the regulation of pericellular hemostasis. Using in vitro cell-based fibrin generation assays, we found that the expression of catalytically active testisin on the cell surface accelerates thrombin-dependent fibrin polymerization, and intriguingly, that it subsequently promotes accelerated fibrinolysis. We find that the testisin-dependent fibrin formation is inhibited by rivaroxaban, a specific inhibitor of the central prothrombin-activating serine protease factor Xa (FXa), demonstrating that cell-surface testisin acts upstream of factor X (FX) to promote fibrin formation at the cell surface. Unexpectedly, testisin was also found to accelerate fibrinolysis by stimulating the plasmin-dependent degradation of fibrin and enhancing plasmin-dependent cell invasion through polymerized fibrin. Testisin was not a direct activator of plasminogen, but it is able to induce zymogen cleavage and the activation of pro-urokinase plasminogen activator (pro-uPA), which converts plasminogen to plasmin. These data identify a new proteolytic component that can regulate pericellular hemostatic cascades at the cell surface, which has implications for angiogenesis, cancer biology, and male fertility.

Improving binding entropy by higher ligand symmetry? - A case study with human matriptase

Understanding different contributions to the binding entropy of ligands is of utmost interest to better predict affinity and the thermodynamic binding profiles of protein-ligand interactions and to develop new strategies for ligand optimization. To these means, the largely neglected effects of introducing higher ligand symmetry, thereby reducing the number of energetically distinguishable binding modes on binding entropy using the human matriptase as a model system, were investigated. A set of new trivalent phloroglucinol-based inhibitors that address the roughly symmetric binding site of the enzyme was designed, synthesized, and subjected to isothermal titration calorimetry. These highly symmetric ligands that can adopt multiple indistinguishable binding modes exhibited high entropy-driven affinity in line with affinity-change predictions.

TMPRSS4, a type II transmembrane serine protease, as a potential therapeutic target in cancer

Proteases are involved in almost all biological processes, implying their importance for both health and pathological conditions. Dysregulation of proteases is a key event in cancer. Initially, research identified their role in invasion and metastasis, but more recent studies have shown that proteases are involved in all stages of cancer development and progression, both directly through proteolytic activity and indirectly via regulation of cellular signaling and functions. Over the past two decades, a novel subfamily of serine proteases called type II transmembrane serine proteases (TTSPs) has been identified. Many TTSPs are overexpressed by a variety of tumors and are potential novel markers of tumor development and progression; these TTSPs are possible molecular targets for anticancer therapeutics. The transmembrane protease serine 4 (TMPRSS4), a member of the TTSP family, is upregulated in pancreatic, colorectal, gastric, lung, thyroid, prostate, and several other cancers; indeed, elevated expression of TMPRSS4 often correlates with poor prognosis. Based on its broad expression profile in cancer, TMPRSS4 has been the focus of attention in anticancer research. This review summarizes up-to-date information regarding the expression, regulation, and clinical relevance of TMPRSS4, as well as its role in pathological contexts, particularly in cancer. It also provides a general overview of epithelial-mesenchymal transition and TTSPs.

Transmembrane serine protease TMPRSS2 implicated in SARS-CoV-2 infection is autoactivated intracellularly and requires N-glycosylation for regulation

Transmembrane protease serine 2 (TMPRSS2) is a membrane-bound protease expressed in many human epithelial tissues, including the airway and lung. TMPRSS2-mediated cleavage of viral spike protein is a key mechanism in severe acute respiratory syndrome coronavirus 2 activation and host cell entry. To date, the cellular mechanisms that regulate TMPRSS2 activity and cell surface expression are not fully characterized. In this study, we examined two major post-translational events, zymogen activation and N-glycosylation, in human TMPRSS2. In experiments with human embryonic kidney 293, bronchial epithelial 16HBE, and lung alveolar epithelial A549 cells, we found that TMPRSS2 was activated via intracellular autocatalysis and that this process was blocked in the presence of hepatocyte growth factor activator inhibitors 1 and 2. By glycosidase digestion and site-directed mutagenesis, we showed that human TMPRSS2 was N-glycosylated. N-glycosylation at an evolutionarily conserved site in the scavenger receptor cysteine-rich domain was required for calnexin-assisted protein folding in the endoplasmic reticulum and subsequent intracellular trafficking, zymogen activation, and cell surface expression. Moreover, we showed that TMPRSS2 cleaved severe acute respiratory syndrome coronavirus 2 spike protein intracellularly in human embryonic kidney 293 cells. These results provide new insights into the cellular mechanism in regulating TMPRSS2 biosynthesis and function. Our findings should help to understand the role of TMPRSS2 in major respiratory viral diseases.

TMPRSS13 zymogen activation, surface localization, and shedding is regulated by proteolytic cleavage within the non-catalytic stem region

TMPRSS13 is a member of the type II transmembrane serine protease (TTSP) family. Here we characterize a novel post-translational mechanism important for TMPRSS13 function: proteolytic cleavage within the extracellular TMPRSS13 stem region located between the transmembrane domain and the first site of N-linked glycosylation at asparagine (N)-250 in the scavenger receptor cysteine rich (SRCR) domain. Importantly, the catalytic competence of TMPRSS13 is essential for stem region cleavage, suggesting an autonomous mechanism of action. Site-directed mutagenesis of the 10 basic amino acids (four arginine and six lysine residues) in this region abrogated zymogen activation and catalytic activity of TMPRSS13, as well as phosphorylation, cell surface expression, and shedding. Mutation analysis of individual arginine residues identified R223, a residue located between the low-density lipoprotein receptor class A domain and the SRCR domain, as important for stem region cleavage. Mutation of R223 causes a reduction in the aforementioned functional processing steps of TMPRSS13. These data provide further insight into the roles of different post-translational modifications as regulators of the function and localization of TMPRSS13. Additionally, the data suggest the presence of complex interconnected regulatory mechanisms that may serve to ensure the proper levels of cell-surface and pericellular TMPRSS13-mediated proteolysis under homeostatic conditions.

Proteases and HPV-Induced Carcinogenesis

Simple Summary

Human papillomavirus (HPV) infection is a sexually transmitted disease with high prevalence worldwide. Although most HPV infections do not lead to cancer, some HPV types are correlated with the majority of cervical cancers, and with some anogenital and oropharyngeal cancers. Moreover, enzymes known as proteases play an essential role in the pathogenic process in HPV-induced carcinogenesis. This review highlights the role of proteases and recent epidemiological data regarding HPV-dependent carcinogenesis.

Abstract

Persistent infection with Human papillomavirus (HPV) is the main etiologic factor for pre-malignant and malignant cervical lesions. Moreover, HPV is also associated with oropharynx and other anogenital carcinomas. Cancer-causing HPV viruses classified as group 1 carcinogens include 12 HPV types, with HPV 16 and 18 being the most prevalent. High-risk HPVs express two oncoproteins, E6 and E7, the products of which are responsible for the inhibition of p53 and pRB proteins, respectively, in human keratinocytes and cellular immortalization. p53 and pRB are pleiotropic proteins that regulate the activity of several signaling pathways and gene expression. Among the important factors that are augmented in HPV-mediated carcinogenesis, proteases not only control processes involved in cellular carcinogenesis but also control the microenvironment. For instance, genetic polymorphisms of matrix metalloproteinase 1 (MMP-1) are associated with carcinoma invasiveness. Similarly, the serine protease inhibitors hepatocyte growth factor activator inhibitor-1 (HAI-1) and -2 (HAI-2) have been identified as prognostic markers for HPV-dependent cervical carcinomas. This review highlights the most crucial mechanisms involved in HPV-dependent carcinogenesis, and includes a section on the proteolytic cascades that are important for the progression of this disease and their impact on patient health, treatment, and survival.

Transmembrane serine protease 2 (TMPRSS2) proteolytically activates the epithelial sodium channel (ENaC) by cleaving the channel's γ-subunit

The epithelial sodium channel (ENaC) is a heterotrimer consisting of α-, β-, and γ-subunits. Channel activation requires proteolytic release of inhibitory tracts from the extracellular domains of α-ENaC and γ-ENaC; however, the proteases involved in the removal of the γ-inhibitory tract remain unclear. In several epithelial tissues, ENaC is coexpressed with the transmembrane serine protease 2 (TMPRSS2). Here, we explored the effect of human TMPRSS2 on human αβγ-ENaC heterologously expressed in Xenopus laevis oocytes. We found that coexpression of TMPRSS2 stimulated ENaC-mediated whole-cell currents by approximately threefold, likely because of an increase in average channel open probability. Furthermore, TMPRSS2-dependent ENaC stimulation was not observed using a catalytically inactive TMPRSS2 mutant and was associated with fully cleaved γ-ENaC in the intracellular and cell surface protein fractions. This stimulatory effect of TMPRSS2 on ENaC was partially preserved when inhibiting its proteolytic activity at the cell surface using aprotinin but was abolished when the γ-inhibitory tract remained attached to its binding site following introduction of two cysteine residues (S155C–Q426C) to form a disulfide bridge. In addition, computer simulations and site-directed mutagenesis experiments indicated that TMPRSS2 can cleave γ-ENaC at sites both proximal and distal to the γ-inhibitory tract. This suggests a dual role of TMPRSS2 in the proteolytic release of the γ-inhibitory tract. Finally, we demonstrated that TMPRSS2 knockdown in cultured human airway epithelial cells (H441) reduced baseline proteolytic activation of endogenously expressed ENaC. Thus, we conclude that TMPRSS2 is likely to contribute to proteolytic ENaC activation in epithelial tissues in vivo.

Function and regulation of corin in physiology and disease

Atrial natriuretic peptide (ANP) is of major importance in the maintenance of electrolyte balance and normal blood pressure. Reduced plasma ANP levels are associated with the increased risk of cardiovascular disease. Corin is a type II transmembrane serine protease that converts the ANP precursor to mature ANP. Corin deficiency prevents ANP generation and alters electrolyte and body fluid homeostasis. Corin is synthesized as a zymogen that is proteolytically activated on the cell surface. Factors that disrupt corin folding, intracellular trafficking, cell surface expression, and zymogen activation are expected to impair corin function. To date, CORIN variants that reduce corin activity have been identified in hypertensive patients. In addition to the heart, corin expression has been detected in non-cardiac tissues, where corin and ANP participate in diverse physiological processes. In this review, we summarize the current knowledge in corin biosynthesis and post-translational modifications. We also discuss tissue-specific corin expression and function in physiology and disease.

Association between preeclampsia and prostasin polymorphism in Pakistani females

Objectives:

To investigate the relationship between a prostasin gene variations and the development of preeclampsia in a Pakistani female population.

Methods:

This was a case-control study carried out at University of Karachi, Karachi, Pakistan between May 2018 and 2019. A single nucleotide polymorphism (SNP) at rs12597511 locus was examined with polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analyses in 76 preeclamptic and 74 normotensive expecting mothers.

Results:

We observed significantly increased risk of preeclampsia associated with the CC genotype of rs12597511 polymorphism as compared to TT (p<0.001, OR=8.08, 95% CI:1.28-31.19) and TT/TC (p<0.001, OR=14.66 and 95% CI: 3.31-65.07) genotypes carriers. Calculation of the allelic distribution revealed a higher frequency of the T allele (82%) among controls; however, the C allele was more prevalent in the preeclamptic group (36%) significantly.

Conclusion:

The significantly higher C allele frequency in the prostasin gene at the rs12597511 locus in the preeclamptic group indicates that the distribution of the C allele of the prostasin gene is a potential risk factor contributing to the development of preeclampsia.

Recombinant Soluble Corin Improves Cardiac Function in Mouse Models of Heart Failure

Background

Corin is a transmembrane protease that activates ANP and BNP (atrial and B‐type natriuretic peptides). Impaired corin expression and function are associated with heart failure. In this study, we characterized a soluble form of corin (sCorin) and examined its effects on cardiac morphology and function in mouse heart failure models.

Methods and Results

sCorin, consisting of the full‐length extracellular fragment of human corin with an engineered activation site, was expressed in Chinese hamster ovary cells, purified from the conditioned medium with affinity chromatography, and characterized in pro‐ANP processing assays in vitro and pharmacokinetic studies in mice. Effects of sCorin on mouse models of heart failure induced by left coronary artery ligation and transverse aortic constriction were assessed by ELISA analysis of plasma markers, histologic examination, and echocardiography. We showed that purified and activated sCorin converted pro‐ANP to ANP that stimulated cGMP production in cultured cells. In mice, intravenously and intraperitoneally administered sCorin had plasma half‐lives of 3.5±0.1 and 8.3±0.3 hour, respectively. In the mouse heart failure models, intraperitoneal injection of sCorin increased plasma ANP, BNP, and cGMP levels; lowered plasma levels of NT‐proANP (N‐terminal‐pro‐ANP), angiotensin II, and aldosterone; reduced cardiac hypertrophy and fibrosis; and improved cardiac function.

Conclusions

We show that sCorin treatment enhanced natriuretic peptide processing and activity, suppressed the renin‐angiotensin‐aldosterone system, and improved cardiac morphology and function in mice with failing hearts.

Hepsin: a multifunctional transmembrane serine protease in pathobiology

Cell membrane-bound serine proteases are important in the maintenance of physiological homeostasis. Hepsin is a type II transmembrane serine protease highly expressed in the liver. Recent studies indicate that hepsin activates prohepatocyte growth factor in the liver to enhance Met signaling, thereby regulating glucose, lipid, and protein metabolism. In addition, hepsin functions in nonhepatic tissues, including the adipose tissue, kidney, and inner ear, to regulate adipocyte differentiation, urinary protein processing, and auditory function, respectively. In mouse models, hepsin deficiency lowers blood glucose, lipid, and protein levels, impairs uromodulin assembly in renal epithelial cells, and causes hearing loss. Elevated hepsin expression has also been found in many cancers. As a type II transmembrane protease, cell surface expression and zymogen activation are essential for hepsin activity. In this review, we discuss the current knowledge regarding hepsin biosynthesis, activation, and functions in pathobiology.

Genetic polymorphism of the prostasin gene in hypertensive pregnant Pakistani females

Objective

The study was performed to investigate the association of hypertension in pregnancy with prostasin gene polymorphism in Pakistani females.

Methods

This case-control study was performed at University of Karachi, Pakistan from April 2018 to May 2019. A total of 160 females, including 90 hypertensives and 70 healthy pregnant females, were recruited by purposive sampling after obtaining informed written consent. Genotyping was performed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).

Results

The frequencies of the TC and CC genotypes were higher in hypertensive pregnant females compared to healthy controls. A significant difference was evident for CC (P=0.012) genotype; however, no significant difference was observed for TC (P=0.49) and TT genotypes (P=0.06) between control and hypertensive groups. The adjusted odds ratio for CC genotype was 6.2 (P=0.025) and 1.48 (P=0.44) for TC genotype compared to the TT genotype. There was a significantly higher prevalence of the C allele of the prostasin gene at rs12597511 in the hypertensive group, suggesting that this allele is a risk factor for hypertension and cardiovascular diseases.

Conclusion

C allele at rs12597511 of prostasin gene demonstrate as a risk factor for having hypertension in pregnancy.

Intracellular autoactivation of TMPRSS11A, an airway epithelial transmembrane serine protease

Type II transmembrane serine proteases (TTSPs) are a group of enzymes participating in diverse biological processes. Some members of the TTSP family are implicated in viral infection. TMPRSS11A is a TTSP expressed on the surface of airway epithelial cells, which has been shown to cleave and activate spike proteins of the severe acute respiratory syndrome (SARS) and the Middle East respiratory syndrome coronaviruses (CoVs). In this study, we examined the mechanism underlying the activation cleavage of TMPRSS11A that converts the one-chain zymogen to a two-chain enzyme. By expression in human embryonic kidney 293, esophageal EC9706, and lung epithelial A549 and 16HBE cells, Western blotting, and site-directed mutagenesis, we found that the activation cleavage of human TMPRSS11A was mediated by autocatalysis. Moreover, we found that TMPRSS11A activation cleavage occurred before the protein reached the cell surface, as indicated by studies with trypsin digestion to remove cell surface proteins, treatment with cell organelle-disturbing agents to block intracellular protein trafficking, and analysis of a soluble form of TMPRSS11A without the transmembrane domain. We also showed that TMPRSS11A was able to cleave the SARS-CoV-2 spike protein. These results reveal an intracellular autocleavage mechanism in TMPRSS11A zymogen activation, which differs from the extracellular zymogen activation reported in other TTSPs. These findings provide new insights into the diverse mechanisms in regulating TTSP activation.