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By Susha Cheriyedath, M.Sc. Jul 31 2023 Reviewed by Benedette Cuffari, M.Sc.

A recent study published in PLOS Pathogens identifies the Leptospira membrane protein L36 (MPL36) as essential for its pathogenesis and, as a result, a potential target for future diagnostics and prophylactics.

Study:  MPL36, a major plasminogen (PLG) receptor in pathogenic Leptospira, has an essential role during infection.  Image Credit: Kateryna Kon / Shutterstock.com Background

The human plasminogen (PLG) system provides a proteolytic substrate for pathogen invasiveness and tissue damage, thereby increasing the virulence of various bacterial species. Sequestration of PLG and activation into plasmin (PLA) is important for bacterial survival, as PLA degrades fibrin clots, extracellular matrix (ECM) molecules, and the host's innate immunological proteins to enable bacteria to spread and evade immune responses ultimately.

Leptospirosis, a life-threatening infectious disease, is a zoonotic disease that accounts for over one million infections and about 60,000 deaths each year throughout the world. In severe forms of leptospirosis, patients will often experience severe hemorrhaging and acute kidney injury.

Leptospira enter the host through injured skin or mucous membranes and subsequently travel through viscous environments to ultimately reach the bloodstream. Thereafter, Leptospira participate in cellular adhesion, which is mediated by various surface proteins that interact with ECM components.

Previous studies indicate that many Leptospira proteins act as PLG receptors, some of which include outer membrane proteins (OMPs) like endostatin-like protein A (LenA), as well as Leptospiral immunoglobulin-like proteins A (LigA), LiGB, and LipL32.

To date, there remains a lack of data on the pathogenesis of leptospirosis, which has prevented the development of sensitive diagnostic instruments and efficient prophylactic treatments. The present study reports that MPL36 binds with PLG, promotes adherence to host cells, and degrades fibrinogen by converting bound PLG to PLA. About the study

The current study utilized Leptospira interrogans serovar Manilae strain L495 and its mutant stains, including Manilae mpl36 mutant complemented strain (Δmpl36+) and Leptospira biflexa serovar Patoc strain Patoc 1. These strains were cultured in Madin-Darby canine kidney (MDCK) cells, following which their growth curves were analyzed using dark-field microscopy, motility, and immunoblot assays.  

Recombinant MPL36 (rMPL36) protein was produced using E. coli expression. Intrinsic tryptophan fluorescence spectroscopy and nickel affinity chromatography evaluated the tertiary structure of rMPL36, rMPL36 aa41-305, and rMPL36 aa41-235. The binding capacity of rMPL36 was determined, and the conversion of PLG bound to rMPL36 into active PLA was evaluated.

The binding of rMPL36 to ECM proteins and PLG was determined by staining for fibronectin, laminin, PLG, and bovine serum albumin (BSA). The pathogenicity of Manilae wildtype (WT) and mutant strains was also evaluated in three-week-old male Golden Syrian hamsters. Related StoriesSARS-CoV-2 spike protein's role in lung injury unraveled: promising new approach uncoveredMitochondrial repair protein discovery may lead to new anti-aging treatmentsSalk researchers uncover molecular mechanisms of HIV drug resistance

The tertiary structure of sporulation-related repeat (SPOR) domains from leptospiral species was predicted using AlphaFold and PyMOL software ClustalX to match MPL36 SPOR domain sequences from various Leptospira species. In vivo data was analyzed using Prism 9, Fisher's exact test, and analysis of variance (ANOVA) to ecludate the mechanisms of rMPL36 binding to host components and BSA. MPL36 is a crucial target for leptopsirosis

The motility assay revealed that, as compared to wild-type cells, mpl36 mutant and complemented strains did not significantly differ in their motility or growth characteristics. Immunofluorescence staining confirmed the subcellular localization of MPL36 in Leptospira as an outer membrane protein in both wild-type and complement cells.

Immunoprecipitation studies revealed that rMPL36 exhibited significant binding to both rLigA and rLigB, whereas no binding was observed between rMPL36 and fibronectin nor laminin.

However, rMPL36 was found to effectively bind to human PLG as compared to other recombinant proteins that were used as positive and negative controls. Within rMPL36, the conserved SPOR domain, which is located at the last 70 amino acids of the protein, is essential for the binding between rMPL36 and PLG.

Hamsters that were infected with the wild-type strain died between eight and nine days following infection with Leptospira. Comparatively, mpl36 mutant hamsters who were infected with 108 leptospires survived without exhibiting any symptoms of leptospirosis, thereby demonstrating the significant role of MPL36 in leptospirosis.

Convalescent sera were obtained from Brazilian individuals with laboratory-confirmed severe leptospirosis. To this end, anti-MPL36 immunoglobulin M (IgM) and IgG were observed in leptospirosis patients’ samples as compared to sera from healthy individuals. Study takeaways

MPL36 is an outer membrane Leptospira protein that is capable of binding to PLG, degrading fibrinogen, and facilitating host infection. Despite these findings, additional research is needed to better understand leptospiral pathogenesis and advance diagnostic and prevention strategies. Journal reference: Zhu, W., Passalia, F. J., Hamond, C., et al. (2023). MPL36, a major plasminogen (PLG) receptor in pathogenic Leptospira, has an essential role during infection. PLOS Pathogens. doi:10.1371/journal.ppat.1011313 https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1011313

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UK content creators demand formal recognition from the government

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UK content creators demand formal recognition from the government

The UK’s YouTubers, TikTok creators and Instagram influencers have been surveyed en masse for the first time ever, and are demanding formal recognition from the government.

The creator economy in the UK is thought to employ around 45,000 people and contribute over £2bn to the country in one year alone, according to the new research by YouTube and Public First.

But, despite all that value, its workers say they feel underappreciated by the authorities.

Max Klyemenko, famous for his Career Ladder videos, wants the government to take creators like himself more seriously. Pic: Youtube
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Max Klyemenko, famous for his Career Ladder videos, wants the government to take creators like himself more seriously. Pic: Youtube

“If you look at the viewership, our channel is not too different from a big media company,” said Max Klymenko, a content creator with more than 10 million subscribers and half a billion monthly views on average.

“If you look at the relevancy, especially among young audiences, I will say that we are more relevant. That said, we don’t really get the same treatment,” he told Sky News.

Fifty-six per cent of the more than 10,000 creators surveyed said they do not think UK creators have a “voice in shaping government policies” that affect them.

Only 7% think they get enough support to access finance, while just 17% think there is enough training and skills development here in the UK.

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Nearly half think their value is not recognised by the broader creative industry.

The creative industries minister, Sir Chris Bryant, said the government “firmly recognises the integral role that creators play” in the UK’s creative industries and the fact that they help “to drive billions into the economy” and support more than 45,000 jobs.

“We understand more can be done to help creators reach their full potential, which is why we are backing them through our new Creative Industries Sector Plan,” he said.

Ben Woods said the government needs to "broaden its lens" to include creators
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Ben Woods said the government needs to “broaden its lens” to include creators

“The UK has got a fantastic history of supporting the creative industries,” said Ben Woods, a creator economy analyst, Midia Research who was not involved in the report.

“Whether you look at the film side, lots of blockbuster films are being shot here, or television, which is making waves on the global stage.

“But perhaps the government needs to broaden that lens a little bit to look at just what’s going on within the creator economy as well, because it is highly valuable, it’s where younger audiences are spending a lot of their time and [the UK is] really good at it.”

Read more from Sky News:
Trump says ‘very wealthy group’ has agreed to buy TikTok in US
Major porn sites to introduce ‘robust’ age verification in UK

According to YouTube, formal recognition would mean creators are factored into official economic impact data reporting, are represented on government creative bodies, and receive creator-specific guidance from HMRC on taxes and finances.

For some, financial guidance and clarity would be invaluable; the ‘creator’ job title seems to cause problems when applying for mortgages or bank loans.

Podcaster David Brown owns a recording studio for creators
Image:
Podcaster David Brown owns a recording studio for creators

“It’s really difficult as a freelancer to get things like mortgages and bank accounts and credit and those types of things,” said podcaster David Brown, who owns a recording studio for creators.

“A lot of people make very good money doing it,” he told Sky News.

“They’re very well supported. They have a lot of cash flow, and they are successful at doing that job. It’s just the way society and banking and everything is set up. It makes it really difficult.”

The creative industries minister said he is committed to appointing a creative freelance champion and increasing support from the British Business Bank in order to “help creators thrive and drive even more growth in the sector”.

The government has already pledged to boost the UK’s creative industries, launching a plan to make the UK the number one destination for creative investment and promising an extra £14bn to the sector by 2035.

These influencers want to make sure they are recognised as part of that.

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Astros’ Alvarez to see hand specialist after setback

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Astros' Alvarez to see hand specialist after setback

DENVER — Houston Astros slugger Yordan Alvarez has experienced a setback in his recovery from a broken right hand and will see a specialist.

Astros general manager Dana Brown said Alvarez felt pain when he arrived Tuesday at the team’s spring training complex in West Palm Beach, Florida, where he had a workout a day earlier. Alvarez also took batting practice Saturday at Daikin Park.

He will be shut down until he’s evaluated by the specialist.

“It’s a tough time going through this with Yordan, but I know that he’s still feeling pain and the soreness in his hand,” Brown said before Tuesday night’s series opener at Colorado, which the Astros won 6-5. “We’re not going to try to push it or force him through anything. We’re just going to allow him to heal and get a little bit more answers as to what steps we take next.”

Alvarez has been sidelined for nearly two months. The injury was initially diagnosed as a muscle strain, but when Alvarez felt pain again while hitting in late May, imaging revealed a small fracture.

The 28-year-old outfielder, who has hit 31 homers or more in each of the past four seasons, had been eyeing a return as soon as this weekend at the Los Angeles Dodgers. Now it’s uncertain when he’ll play.

“We felt like he was close because he had felt so good of late,” Brown said, “but this is certainly news that we didn’t want.”

Also Tuesday, the Astros officially placed shortstop Jeremy Peña on the 10-day injured list with a fractured rib and recalled infielder Shay Whitcomb from Triple-A Sugar Land.

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Springer’s 7 RBIs help Jays pile on Yankees late

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Springer's 7 RBIs help Jays pile on Yankees late

George Springer had a career-high seven RBIs, including his ninth grand slam, and the Toronto Blue Jays celebrated Canada Day by beating the Yankees 12-5 on Tuesday and closing within one game of American League East-leading New York.

The seven RBIs are tied for the second most by any Blue Jays player in a home game, behind Edwin Encarnación (nine RBIs in 2015), according to ESPN Research.

Andrés Giménez had a go-ahead, three-run homer for the Blue Jays, who overcame a 2-0 deficit against Max Fried. After the Yankees tied the score 4-4 in the seventh, Toronto broke open the game in the bottom half against a reeling Yankees bullpen.

Springer went 3-for-4, starting the comeback with a solo homer in the fourth against Fried and boosting the lead to 9-5 with the slam off Luke Weaver after Ernie Clement‘s go-ahead single off shortstop Anthony Volpe‘s glove. Springer has 13 homers this season.

Toronto won the first two games of the four-game series and closed within one game of the Yankees for the first time since before play on April 20.

New York went 2-for-17 with runners in scoring position, dropping to 3-for-24 in the series, while the Blue Jays were 5-for-7. After going 13-14 in June, the Yankees fell to 10-14 against AL East rivals.

The Associate Press contributed to this report.

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