<div data-thumb=”https://scx1.b-cdn.net/csz/news/tmb/2023/a-breakthrough-in-unde.jpg” data-src=”https://scx2.b-cdn.net/gfx/news/hires/2023/a-breakthrough-in-unde.jpg” data-sub-html=”CMT activity is not divalent metal ion dependent. a, Schematic of CMT-mediated tryptophan C-mannosylation of secretory and transmembrane proteins in the endoplasmic reticulum (ER). Nascent polypeptide chains (pink line) containing the WxxW/C sequon (pink boxes) are mannosylated by CMT using Dol-P-Man (mannosyl group depicted in green) as donor substrate, thereby forming the depicted C-glycosidic bond. Glycopeptides are subsequently folded and secreted via the Golgi apparatus. b, In vitro C-mannosylation reaction using purified CMT CeDPY19. Tricine–SDS–PAGE was used to separate fluorescently labeled acceptor peptide upon mannosylation or unmodified, n = 1 independent replicates. c, LC–MS analysis of in vitro C-mannosylation reaction, demonstrating the attachment of a single hexose to the fluorescently labeled acceptor peptide, n = 1 independent replicates. d, Tricine–SDS–PAGE analysis of in vitro C-mannosylation reaction in presence of the divalent metal ions MnCl2 and MgCl2 as well as in the absence of divalent metal ions and with CeDPY19 preincubated with the metal ion chelator EDTA, demonstrating that CMT activity is unaffected by the absence of divalent metal ions, n = 1 independent replicates. Credit: Nature Chemical Biology (2023). DOI: 10.1038/s41589-022-01219-9″>
CMT activity is not divalent metal ion dependent. a, Schematic of CMT-mediated tryptophan C-mannosylation of secretory and transmembrane proteins in the endoplasmic reticulum (ER). Nascent polypeptide chains (pink line) containing the WxxW/C sequon (pink boxes) are mannosylated by CMT using Dol-P-Man (mannosyl group depicted in green) as donor substrate, thereby forming the depicted C-glycosidic bond. Glycopeptides are subsequently folded and secreted via the Golgi apparatus. b, In vitro C-mannosylation reaction using purified CMT CeDPY19. Tricine–SDS–PAGE was used to separate fluorescently labeled acceptor peptide upon mannosylation or unmodified, n = 1 independent replicates. c, LC–MS analysis of in vitro C-mannosylation reaction, demonstrating the attachment of a single hexose to the fluorescently labeled acceptor peptide, n = 1 independent replicates. d, Tricine–SDS–PAGE analysis of in vitro C-mannosylation reaction in presence of the divalent metal ions MnCl2 and MgCl2 as well as in the absence of divalent metal ions and with CeDPY19 preincubated with the metal ion chelator EDTA, demonstrating that CMT activity is unaffected by the absence of divalent metal ions, n = 1 independent replicates. Credit: Nature Chemical Biology (2023). DOI: 10.1038/s41589-022-01219-9
In multicellular organisms, there are three types of protein glycosylation. N-glycosylation, O-mannosylation and C-mannosylation. All of these processes take place in the endoplasmic reticulum, and in all of them enzymes attach sugar residues to specific sites in newly forming protein.
While N- and O-glycosylation are well studied, the third form, C-mannosylation of tryptophan side chains, has long been a mystery to researchers. Although 20 percent of all secretory proteins, as well as membrane proteins, are affected by it, it was unclear until recently what the change was for, how the specific protein sequences are recognized and how the associated enzyme reaction is chemically possible at all.
In an international collaboration, researchers from ETH Zurich, the Walter and Eliza Hall Institute of Medical Research (WEHI) in Australia, the University of Chicago and the University of Bern have now elucidated the structure and function of the responsible enzyme, ‘tryptophan C-mannosyltransferase’ (CMT). The corresponding study was published in the latest issue of the journal Nature Chemical Biology.
CMT is a member of the category C (GT-C) glycosyltransferase enzymes, one of the three glycosyltransferase superfamilies. The most prominent member is oligosaccharyltransferase (OST), which is responsible for N-glycosylation.
Similar to the OST, the CMT also recognizes highly specific sequences in proteins, with the difference, however, that in mammals four different CMTs occur simultaneously, which also recognize different protein sequences.
Sugars help immuno-receptors to the cell surface
Only in recent years, the necessary tools, such as special antibodies and mass spectrometry test methods, were developed in order to be able to investigate the extent of C-mannosylation. It was shown that this process occurs almost exclusively where cell-cell communication is essential, especially in cytokine receptors of the immune system and adhesion GPCRs. The latter serve as “sensory antennae” for growing neurons that make their way through the brain.
“The topic is red-hot, especially for our understanding of the cell-cell communication of the immune system,” explains Kaspar Locher, Professor of Structural Biology at ETH Zurich: “Signaling molecules such as cytokines direct the immune response during an infection. While these and their associated receptors have been intensively studied for decades, it has long been neglected that C-mannosylation determines whether a cytokine receptor reaches the cell surface to exert its function.”
“With our insights into the structure of the enzymes involved, we now have a near-complete understanding of how C-mannosylation gets to these receptors,” adds study first author Joël Bloch, former senior scientist in Locher’s group.
Tailor-made molecular construction kit
The ETH researchers succeeded in producing the CMT enzyme in its pure form. With the help of chemists from WEHI (AUS) and the University of Bern, they built customized molecules that mimic CMT-specific protein sequences and sugar substrates. This allowed them to test the enzyme for its specific properties in the test tube for the first time.
The researchers quickly realized that the enzyme chemistry of CMT must be novel and completely different from that of OST. “In such a case, we can only find out the mechanism of an enzyme using high-resolution structural elucidation. The problem, however, was that CMT could not be crystallized until now and had too little mass for cryo-EM, because this technique is particularly difficult to apply to proteins below 100 kDa,” Locher explains.
Antibody enables high-resolution electron microscopy
A trick finally brought the breakthrough: In collaboration with researchers from the University of Chicago, the ETH scientists produced a synthetic antibody that binds specifically to the CMT. This antibody increased the mass of the enzyme so much that its structure could be elucidated with the help of cryo-EM. With the help of the cryo-EM structures, the group led by Kaspar Locher was finally able to decipher how the different CMT variants recognize different protein sequences.
Based on these insights, the researchers could now predict more precisely which proteins in humans carry the modification. From this, they hope to be able to capture the ‘C-mannosyl proteome’ in the near future.
By deciphering the peptide binding mechanism of CMTs, the researchers also hope to make progress in the production of CMT-specific inhibitors. Such molecules could contribute to advances in drug production, such as those to combat the malaria pathogen Plasmodium falciparum, which has its own CMT and needs it to attach to the host.
The sequence and organ specificity of the human CMT variant CMT2 could also be used, as it plays a key role in sperm development. The new findings could therefore be used to develop CMT2 inhibitors as contraceptives for men.
A novel enzyme mechanism
Another enigma for scientists was the enzymatic mechanism of CMT. This creates a unique carbon-carbon bond between protein and sugar. Using a custom-made CMT inhibitor molecule, the scientists were able to “capture” CMT in the middle of a glycosyl transfer reaction and elucidate a cryo-EM structure of it.
This allowed them to visualize the CMT reaction mechanism: a previously unknown form of electrophilic aromatic substitution enabled by precisely arranged side chains. Such insights could contribute to the development of designer enzymes that catalyze bonds between carbon atoms.
Evolutionarily conserved protective mechanism in glycosyltransferases
With a total of four different structures of the CMT, the scientists succeeded for the first time in visualizing a practically complete catalytic cycle of an enzyme of the GT-C superfamily.
In the process, they uncovered an astonishing mechanism: The sugar substrates of the CMT are complex to produce due to their lipid binding and are therefore particularly valuable. As it turned out, the CMT initially binds them in a non-reactive protected binding pocket. Only when the protein or peptide to be modified docks onto the CMT is the sugar substrate shifted by a peptide sensor and brought into a highly reactive state.
The scientists assume that this mechanism is evolutionarily conserved in GT-C enzymes and prevents valuable substrate molecules from being prematurely consumed. “Having uncovered the general architecture of GT-C enzymes three years ago, we now have a holistic understanding of their enzyme chemistry. It is another milestone in glycobiology,” explains Locher.
More information:
Joël S. Bloch et al, Structure, sequon recognition and mechanism of tryptophan C-mannosyltransferase, Nature Chemical Biology (2023). DOI: 10.1038/s41589-022-01219-9
Citation:
A breakthrough in understanding the sugar biology of multicellular organisms (2023, January 16)
retrieved 16 January 2023
from https://phys.org/news/2023-01-breakthrough-sugar-biology-multicellular.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.
Skinstitut Holiday Gift Kits take the stress out of gifting
Toronto, October 31, 2024 – Beauty gifts are at the top of holiday wish lists this year, and Laser Clinics Canada, a leader in advanced beauty treatments and skincare, is taking the pressure out of seasonal shopping. Today, Laser Clincs Canada announces the arrival of its 2024 Holiday Gift Kits, courtesy of Skinstitut, the exclusive skincare line of Laser Clinics Group.
In time for the busy shopping season, the limited-edition Holiday Gifts Kits are available in Laser Clinics locations in the GTA and Ottawa. Clinics are conveniently located in popular shopping centers, including Hillcrest Mall, Square One, CF Sherway Gardens, Scarborough Town Centre, Rideau Centre, Union Station and CF Markville. These limited-edition Kits are available on a first come, first served basis.
“These kits combine our best-selling products, bundled to address the most relevant skin concerns we’re seeing among our clients,” says Christina Ho, Senior Brand & LAM Manager at Laser Clinics Canada. “With several price points available, the kits offer excellent value and suit a variety of gift-giving needs, from those new to cosmeceuticals to those looking to level up their skincare routine. What’s more, these kits are priced with a savings of up to 33 per cent so gift givers can save during the holiday season.
There are two kits to select from, each designed to address key skin concerns and each with a unique theme — Brightening Basics and Hydration Heroes.
Brightening Basics is a mix of everyday essentials for glowing skin for all skin types. The bundle comes in a sleek pink, reusable case and includes three full-sized products: 200ml gentle cleanser, 50ml Moisture Defence (normal skin) and 30ml1% Hyaluronic Complex Serum. The Brightening Basics kit is available at $129, a saving of 33 per cent.
Hydration Heroes is a mix of hydration essentials and active heroes that cater to a wide variety of clients. A perfect stocking stuffer, this bundle includes four deluxe products: Moisture 15 15 ml Defence for normal skin, 10 ml 1% Hyaluronic Complex Serum, 10 ml Retinol Serum and 50 ml Expert Squalane Cleansing Oil. The kit retails at $59.
In addition to the 2024 Holiday Gifts Kits, gift givers can easily add a Laser Clinic Canada gift card to the mix. Offering flexibility, recipients can choose from a wide range of treatments offered by Laser Clinics Canada, or they can expand their collection of exclusive Skinstitut products.
Brightening Basics 2024 Holiday Gift Kit by Skinstitut, available exclusively at Laser Clincs Canada clinics and online at skinstitut.ca.
Hydration Heroes 2024 Holiday Gift Kit by Skinstitut – available exclusively at Laser Clincs Canada clinics and online at skinstitut.ca.
LONDON (AP) — Most people have accumulated a pile of data — selfies, emails, videos and more — on their social media and digital accounts over their lifetimes. What happens to it when we die?
It’s wise to draft a will spelling out who inherits your physical assets after you’re gone, but don’t forget to take care of your digital estate too. Friends and family might treasure files and posts you’ve left behind, but they could get lost in digital purgatory after you pass away unless you take some simple steps.
Here’s how you can prepare your digital life for your survivors:
Apple
The iPhone maker lets you nominate a “ legacy contact ” who can access your Apple account’s data after you die. The company says it’s a secure way to give trusted people access to photos, files and messages. To set it up you’ll need an Apple device with a fairly recent operating system — iPhones and iPads need iOS or iPadOS 15.2 and MacBooks needs macOS Monterey 12.1.
For iPhones, go to settings, tap Sign-in & Security and then Legacy Contact. You can name one or more people, and they don’t need an Apple ID or device.
You’ll have to share an access key with your contact. It can be a digital version sent electronically, or you can print a copy or save it as a screenshot or PDF.
Take note that there are some types of files you won’t be able to pass on — including digital rights-protected music, movies and passwords stored in Apple’s password manager. Legacy contacts can only access a deceased user’s account for three years before Apple deletes the account.
Google
Google takes a different approach with its Inactive Account Manager, which allows you to share your data with someone if it notices that you’ve stopped using your account.
When setting it up, you need to decide how long Google should wait — from three to 18 months — before considering your account inactive. Once that time is up, Google can notify up to 10 people.
You can write a message informing them you’ve stopped using the account, and, optionally, include a link to download your data. You can choose what types of data they can access — including emails, photos, calendar entries and YouTube videos.
There’s also an option to automatically delete your account after three months of inactivity, so your contacts will have to download any data before that deadline.
Facebook and Instagram
Some social media platforms can preserve accounts for people who have died so that friends and family can honor their memories.
When users of Facebook or Instagram die, parent company Meta says it can memorialize the account if it gets a “valid request” from a friend or family member. Requests can be submitted through an online form.
The social media company strongly recommends Facebook users add a legacy contact to look after their memorial accounts. Legacy contacts can do things like respond to new friend requests and update pinned posts, but they can’t read private messages or remove or alter previous posts. You can only choose one person, who also has to have a Facebook account.
You can also ask Facebook or Instagram to delete a deceased user’s account if you’re a close family member or an executor. You’ll need to send in documents like a death certificate.
TikTok
The video-sharing platform says that if a user has died, people can submit a request to memorialize the account through the settings menu. Go to the Report a Problem section, then Account and profile, then Manage account, where you can report a deceased user.
Once an account has been memorialized, it will be labeled “Remembering.” No one will be able to log into the account, which prevents anyone from editing the profile or using the account to post new content or send messages.
X
It’s not possible to nominate a legacy contact on Elon Musk’s social media site. But family members or an authorized person can submit a request to deactivate a deceased user’s account.
Passwords
Besides the major online services, you’ll probably have dozens if not hundreds of other digital accounts that your survivors might need to access. You could just write all your login credentials down in a notebook and put it somewhere safe. But making a physical copy presents its own vulnerabilities. What if you lose track of it? What if someone finds it?
Instead, consider a password manager that has an emergency access feature. Password managers are digital vaults that you can use to store all your credentials. Some, like Keeper,Bitwarden and NordPass, allow users to nominate one or more trusted contacts who can access their keys in case of an emergency such as a death.
But there are a few catches: Those contacts also need to use the same password manager and you might have to pay for the service.
___
Is there a tech challenge you need help figuring out? Write to us at onetechtip@ap.org with your questions.
The Canadian Paediatric Society says doctors should regularly screen children for reading difficulties and dyslexia, calling low literacy a “serious public health concern” that can increase the risk of other problems including anxiety, low self-esteem and behavioural issues, with lifelong consequences.
New guidance issued Wednesday says family doctors, nurses, pediatricians and other medical professionals who care for school-aged kids are in a unique position to help struggling readers access educational and specialty supports, noting that identifying problems early couldhelp kids sooner — when it’s more effective — as well as reveal other possible learning or developmental issues.
The 10 recommendations include regular screening for kids aged four to seven, especially if they belong to groups at higher risk of low literacy, including newcomers to Canada, racialized Canadians and Indigenous Peoples. The society says this can be done in a two-to-three-minute office-based assessment.
Other tips encourage doctors to look for conditions often seen among poor readers such as attention-deficit hyperactivity disorder; to advocate for early literacy training for pediatric and family medicine residents; to liaise with schools on behalf of families seeking help; and to push provincial and territorial education ministries to integrate evidence-based phonics instruction into curriculums, starting in kindergarten.
Dr. Scott McLeod, one of the authors and chair of the society’s mental health and developmental disabilities committee, said a key goal is to catch kids who may be falling through the cracks and to better connect families to resources, including quicker targeted help from schools.
“Collaboration in this area is so key because we need to move away from the silos of: everything educational must exist within the educational portfolio,” McLeod said in an interview from Calgary, where he is a developmental pediatrician at Alberta Children’s Hospital.
“Reading, yes, it’s education, but it’s also health because we know that literacy impacts health. So I think that a statement like this opens the window to say: Yes, parents can come to their health-care provider to get advice, get recommendations, hopefully start a collaboration with school teachers.”
McLeod noted that pediatricians already look for signs of low literacy in young children by way of a commonly used tool known as the Rourke Baby Record, which offers a checklist of key topics, such as nutrition and developmental benchmarks, to cover in a well-child appointment.
But he said questions about reading could be “a standing item” in checkups and he hoped the society’s statement to medical professionals who care for children “enhances their confidence in being a strong advocate for the child” while spurring partnerships with others involved in a child’s life such as teachers and psychologists.
The guidance said pediatricians also play a key role in detecting and monitoring conditions that often coexist with difficulty reading such as attention-deficit hyperactivity disorder, but McLeod noted that getting such specific diagnoses typically involves a referral to a specialist, during which time a child continues to struggle.
He also acknowledged that some schools can be slow to act without a specific diagnosis from a specialist, and even then a child may end up on a wait list for school interventions.
“Evidence-based reading instruction shouldn’t have to wait for some of that access to specialized assessments to occur,” he said.
“My hope is that (by) having an existing statement or document written by the Canadian Paediatric Society … we’re able to skip a few steps or have some of the early interventions present,” he said.
McLeod added that obtaining specific assessments from medical specialists is “definitely beneficial and advantageous” to know where a child is at, “but having that sort of clear, thorough assessment shouldn’t be a barrier to intervention starting.”
McLeod said the society was partly spurred to act by 2022’s “Right to Read Inquiry Report” from the Ontario Human Rights Commission, which made 157 recommendations to address inequities related to reading instruction in that province.
He called the new guidelines “a big reminder” to pediatric providers, family doctors, school teachers and psychologists of the importance of literacy.
“Early identification of reading difficulty can truly change the trajectory of a child’s life.”
This report by The Canadian Press was first published Oct. 23, 2024.
