Folding Pathway Mediated by an Intramolecular Chaperone: Intrinsically Unstructured Propeptide Modulates Stochastic Activation of Subtilisin

Subbian, Ezhilkani; Yabuta, Yukihiro; Shinde, Ujwal

doi:10.1016/j.jmb.2005.01.028

Cited by 39 publications

(67 citation statements)

References 69 publications

(102 reference statements)

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“…During this stage, the IMC remains associated with the protease and serves as a temporary inhibitor of protease activity (47). Finally, through a second autoproteolytic event, the IMC is released and degraded, which results in an active, mature protease (48)(49)(50). We detected both the proenzyme and mature forms of StmPr1 and StmPr2 in strain K279a supernatant.…”

Section: Discussionmentioning

confidence: 89%

Type II Secretion-Dependent Degradative and Cytotoxic Activities Mediated by Stenotrophomonas maltophilia Serine Proteases StmPr1 and StmPr2

2015

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Stenotrophomonas maltophilia is an emerging opportunistic pathogen that primarily causes pneumonia and bacteremia in immunocompromised individuals. We recently reported that S. maltophilia strain K279a encodes the Xps type II secretion system and that Xps promotes rounding, actin rearrangement, detachment, and death in the human lung epithelial cell line A549. Here, we show that Xps-dependent cell rounding and detachment occur with multiple human and murine cell lines and that serine protease inhibitors block Xps-mediated rounding and detachment of A549 cells. Using genetic analysis, we determined that the serine proteases StmPr1 and StmPr2, which were confirmed to be Xps substrates, are predominantly responsible for secreted proteolytic activities exhibited by strain K279a, as well as the morphological and cytotoxic effects on A549 cells. Supernatants from strain K279a also promoted the degradation of type I collagen, fibrinogen, and fibronectin in a predominantly Xps-and protease-dependent manner, although some Xps-independent degradation of fibrinogen was observed. Finally, Xps, and predominantly StmPr1, degraded interleukin 8 (IL-8) secreted by A549 cells during coculture with strain K279a. Our findings indicate that while StmPr1 and StmPr2 are predominantly responsible for A549 cell rounding, extracellular matrix protein degradation, and IL-8 degradation, additional Xps substrates also contribute to these activities. Altogether, our data provide new insight into the virulence potential of the S. maltophilia Xps type II secretion system and its StmPr1 and StmPr2 substrates. The Gram-negative bacterium Stenotrophomonas maltophilia, prevalent in the aqueous environment, is now emerging as a prominent opportunistic and nosocomial pathogen (1, 2). S. maltophilia infects an array of host tissues and organs, including the respiratory tract, blood, bone, soft tissue, eye, urinary tract, heart, and brain. However, pneumonia is the most common infection associated with S. maltophilia, followed by bloodstream infection as the second most common (1, 2). S. maltophilia, though relatively nonvirulent for healthy individuals, can cause serious infection in immunocompromised individuals. Therefore, S. maltophilia poses the biggest threat for patients with severe burns, cystic fibrosis, and HIV, as well as those undergoing chemotherapy or immunosuppressive therapy (3). Prolonged hospitalization in intensive care units and long-term antibiotic treatment are also considered risk factors for developing pneumonia and bacteremia, for which mortality rates can range from 23 to 77% and 14 to 69%, respectively (1, 4). Community-acquired S. maltophilia infections, especially in the high-risk populations mentioned, have been reported (5), and recently, a communityacquired skin infection was reported for the first time in an immunocompetent individual (6). The multidrug-resistant nature of S. maltophilia makes treatment of infections highly difficult (7), and in recent years, an increased resistance to the preferred antibiotic trimeth...

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Section: Discussionmentioning

confidence: 89%

Type II Secretion-Dependent Degradative and Cytotoxic Activities Mediated by Stenotrophomonas maltophilia Serine Proteases StmPr1 and StmPr2

2015

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“…However, many propeptides remain functional as folding catalysts when added in trans (17,20,37,45). This folding process is best studied in the serine proteases subtilisin and ␣-lytic protease (34,36,43). The propeptide guides folding of the catalytic domain through a nonnative folding intermediate to an unprocessed native fold by lowering the free energy required to achieve the native state (1,27,34).…”

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confidence: 99%

The Propeptide of the Metalloprotease ofListeria monocytogenesControls Compartmentalization of the Zymogen during Intracellular Infection

et al. 2009

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Integral to the virulence of the intracellular bacterial pathogen Listeria monocytogenes is its metalloprotease (Mpl). Mpl regulates the activity and compartmentalization of the bacterial broad-range phospholipase C (PC-PLC). Mpl is secreted as a proprotein that undergoes intramolecular autocatalysis to release its catalytic domain. In related proteases, the propeptide serves as a folding catalyst and can act either in cis or in trans. Propeptides can also influence protein compartmentalization and intracellular trafficking or decrease folding kinetics. In this study, we aimed to determine the role of the Mpl propeptide by monitoring the behavior of Mpl synthesized in the absence of its propeptide (Mpl⌬pro) and of two Mpl single-site mutants with unstable propeptides: Mpl(H75V) and Mpl(H95L). We observed that all three Mpl mutants mediate PC-PLC activation when bacteria are grown on semisolid medium, but to a lesser extent than wild-type Mpl, indicating that, although not essential, the propeptide enhances the production of active Mpl. However, the mutant proteins were not functional in infected cells, as determined by monitoring PC-PLC maturation and compartmentalization. This defect could not be rescued by providing the propeptide in trans to the mpl⌬pro mutant. We tested the compartmentalization of Mpl during intracellular infection and observed that the mutant Mpl species were aberrantly secreted in the cytosol of infected cells. These data indicated that the propeptide of Mpl serves to maintain bacterium-associated Mpl and that this localization is essential to the function of Mpl during intracellular infection.

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“…However, not all propeptides function as intramolecular protease inhibitors. For some proteases, the propeptides act primarily as intramolecular protein folding chaperones that are needed for protease activity (Subbian et al, 2005;Schilling et al, 2009). Moreover, the bromelains that accumulate in the stem and fruit lack the propeptide (Yamada et al, 1976;Ritonja et al, 1989;Harrach et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

An Extended AE-Rich N-Terminal Trunk in Secreted Pineapple Cystatin Enhances Inhibition of Fruit Bromelain and Is Posttranslationally Removed during Ripening

2009

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Phytocystatins are potent inhibitors of cysteine proteases and have been shown to participate in senescence, seed and organ biogenesis, and plant defense. However, phytocystatins are generally poor inhibitors of the cysteine protease, bromelain, of pineapple (Ananas comosus). Here, we demonstrated that pineapple cystatin, AcCYS1, inhibited (.95%) stem and fruit bromelain. AcCYS1 is a unique cystatin in that it contains an extended N-terminal trunk (NTT) of 63 residues rich in alanine and glutamate. A signal peptide preceding the NTT is processed in vitro by microsomal membranes giving rise to a 27-kD species. AcCYS1 mRNA was present in roots and leaves but was most abundant in fruit. Using immunofluorescence and immunoelectron microscopy with an AcCYS1-specific antiserum, AcCYS1 was found in the apoplasm. Immunoblot analysis identified a 27-kD protein in fruit, roots, and leaves and a 15-kD species in mature ripe fruit. Ripe fruit extracts proteolytically removed the NTT of 27-kD AcCYS1 in vitro to produce the 15-kD species. Mass spectrometry analysis was used to map the primary cleavage site immediately after a conserved critical glycine-94. The AE-rich NTT was required to inhibit fruit and stem bromelain (.95%), whereas its removal decreased inhibition to 20% (fruit) and 80% (stem) and increased the dissociation equilibrium constant by 1.8-fold as determined by surface plasmon resonance assays. We propose that proteolytic removal of the NTT results in the decrease of the inhibitory potency of AcCYS1 against fruit bromelain during fruit ripening to increase tissue proteolysis, softening, and degradation.

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Folding Pathway Mediated by an Intramolecular Chaperone: Intrinsically Unstructured Propeptide Modulates Stochastic Activation of Subtilisin

Cited by 39 publications

References 69 publications

Type II Secretion-Dependent Degradative and Cytotoxic Activities Mediated by Stenotrophomonas maltophilia Serine Proteases StmPr1 and StmPr2

Type II Secretion-Dependent Degradative and Cytotoxic Activities Mediated by Stenotrophomonas maltophilia Serine Proteases StmPr1 and StmPr2

The Propeptide of the Metalloprotease ofListeria monocytogenesControls Compartmentalization of the Zymogen during Intracellular Infection

An Extended AE-Rich N-Terminal Trunk in Secreted Pineapple Cystatin Enhances Inhibition of Fruit Bromelain and Is Posttranslationally Removed during Ripening

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