Unlike most other proteins, tau does not have a clearly defined structure: Tau is an “intrinsically disordered protein” that can take many shapes. “We can imagine it like a rope: it can be sometimes elongated, sometimes bent, sometimes looped,” says Malte Drescher. Despite all the variance, tau tends to assume a characteristically recurved structure, comparable to the shape of a paper clip.

An unusual molecular chaperone

A peculiarity occurs as soon as the chaperone HSP-90 (“Heat Shock Protein 90”) encounters tau. “Normally, it is the job of chaperones to bring newly produced proteins into the correct form. Thus they exert a helper function in the development of protein structure. We were wondering: What might their helper function be in an intrinsically disordered protein such as tau?” summarizes Drescher.

Using structural analyses, Drescher and his team were able to show that the chaperone causes the paper clip conformation of tau to open: It folds the “brackets” of the paper clip outwards. “The area in the middle of the paper clip is thus exposed and made accessible. This area is known to be responsible for aggregation, i.e. for attachment of further tau proteins to the molecule,” explains biophysicist Sabrina Weickert, lead author of the study and a doctoral researcher under Malte Drescher’s supervision. In their unfolded form, tau molecules can therefore be stacked on top of each other with a perfect fit (oligomerization).

“This oligomerization by HSP-90 came as a big surprise,” explains Malte Drescher: “A chaperone is actually responsible for exactly the opposite: It is supposed to bring a protein into a defined form and under no circumstances contribute to the formation of a ‘protein pile’,” says Drescher.

Responsible for Alzheimer’s or secretly a defence mechanism?

Is the presence of the chaperone thus a pre-requisite for the formation of Alzheimer fibrils? Is the chaperone, of all molecules, ultimately the one that causes the development of Alzheimer’s disease? The researchers will pursue this question in further studies. However, Malte Drescher suspects precisely the opposite: “I would argue exactly the other way round: It could even be a trick the body does to prevent Alzheimer’s,” Drescher contemplates. The tau oligomers produced by HSP-90 have one crucial peculiarity: They do not continue to grow to form the typical pronounced Alzheimer fibrils.

“The oligomerization by HSP-90 might possibly be a defence mechanism in which the chaperone forces the tau proteins into the form of small oligomer layers. Although this is not advantageous, it effectively prevents formation of longer, Alzheimer-typical fibrils,” Drescher suggests. Should this assumption prove true, the chaperone would fulfil its stated purpose: In this case, it would prevent the development of long Alzheimer fibrils by making a gambit and binding tau into smaller, less dangerous stacks.

Spin labels

The protein tau is only a few nanometres in size, i.e. a billionth of a metre, and is not visible to the naked eye or light microscopes. Otherwise typical experiments for structure determination such as X-ray structure analysis fail, because tau as an intrinsically disordered protein is so extremely flexible. In order to determine the structural changes of the protein anyway, the researchers therefore resorted to a sophisticated method: They attached tiny probe molecules, “spin labels,” to key positions of the molecule, including the outer “brackets” of the paper clip conformation. “The probes are magnetic and sense each other. We measure the interaction between the probes and can thus determine the distance between their positions,” explains Malte Drescher. In this way, they can indirectly detect the conformation of the molecule and its structural changes.

The series of experiments took place in vitro, with purified tau and HSP-90 molecules in the test tube. “We now want to bring the experiment into the cell in order to observe the biochemical mechanism under the real-world conditions inside a cell,” says Malte Drescher, giving an outlook on future research work. The long-term goal is to better understand the development of Alzheimer’s disease and to find methods to prevent it.

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More than 325 dental patients who had teeth pulled were asked to rate their pain and satisfaction within six months of extraction. Roughly half of the study’s patients who had surgical extraction and 39% who had routine extraction were prescribed opioids.

The U-M researchers compared the pain and satisfaction of those who used opioids to those who didn’t.

“I feel like the most important finding is that patient satisfaction with pain management was no different between the opioid group and non-opioid group, and it didn’t make a difference whether it was surgical or routine extraction,” said study co-author Romesh Nalliah, clinical professor and associate dean for patient services at the U-M School of Dentistry.

Surprisingly, patients in the opioid group actually reported worse pain than the non-opioid group for both types of extractions, Nalliah said.

The researchers also found that roughly half of the opioids prescribed remained unused in both surgical and nonsurgical extractions. This could put patients or their loved ones at risk of future misuse of opioids if leftover pills are not disposed of properly.

The findings are scheduled to appear March 13 in JAMA Network Open.

“The real-world data from this study reinforces the previously published randomized-controlled trials showing opioids are no better than acetaminophen and nonsteroidal anti-inflammatory drugs for pain after dental extraction,” said study co-author Chad Brummett, director of the Division of Pain Research and of Clinical Research in the Department of Anesthesiology at Michigan Medicine, U-M’s academic medical center.

Brummett co-directs the Michigan Opioid Prescribing Engagement Network, or Michigan OPEN, which has developed, tested and shared guidelines for the use of opioids in patients with acute pain from surgery and medical procedures.

“These data support the Michigan OPEN prescribing recommendations calling for no opioids for the majority of patients after dental extractions, including wisdom teeth extraction,” he said.

The results have big implications for both patients and dentists, and suggest prescribing practices need an overhaul, Brummett and Nalliah said.

The American Dental Association suggests limiting opioid prescribing to seven days’ supply, but Nalliah believes that’s too high.

“I think we can almost eliminate opioid prescribing from dental practice. Of course, there are going to be some exceptions, like patients who can’t tolerate nonsteroidal anti-inflammatories,” he said. “I would estimate we can reduce opioid prescribing to about 10% of what we currently prescribe as a profession.”

For dentists, many of whom are sole proprietors, this new information means they needn’t worry so much about unhappy patients changing practices if they aren’t prescribed strong opioids. Alternatives such as nonsteroidal anti-inflammatory drugs or acetaminophen appear to control pain better, and patient satisfaction remains high.

Nalliah gives two possible reasons for this. First, dentists may have prescribed opioids in only the toughest cases, which would have resulted in more pain regardless.

“Or alternatively, and this is the reason I tend to accept, is that our study concurs with previous studies that suggest opioids are not the most effective analgesic for acute dental pain,” Nalliah said.

“Dentists are torn between wanting to satisfy patients and grow business and limiting their opioid prescribing in light of the current crisis. I think it’s an extremely liberating finding for dentists who can worry more about the most effective pain relief rather than overprescribing for opioids.”

Dentists account for about 6% to 6.5% of U.S. opioid prescriptions — a relatively small amount. But the study notes that dentists are among the most common prescribers for minors, and for many patients, dental opioid prescriptions are their first exposure.

“Throughout our lifetime, squames are continually being shed from the skin surface and replaced by inner cells moving outward,” says Elaine Fuchs, Rockefeller’s Rebecca C. Lancefield Professor, whose lab recently shed new light onto this process. “We’ve identified the mechanism that allows skin cells to sense new changes in their environment and very quickly deploy instructions to drive squame formation.”

Conducted in mice and described in Science, the research also provides insight into how errors in this mechanism might lead to skin conditions like atopic dermatitis and psoriasis.

Like oil and vinegar

The skin’s epidermis consists of an inner layer of stem cells that periodically stop dividing and move outward, toward the body surface. As the cells transit through subsequent layers, they face the increasingly harsh extremes of our environment, like variations in temperature. In the very last step, as they approach the surface, the cells’ nuclei and organelles are suddenly lost in the dramatic transformation into squames.

Felipe Garcia Quiroz, a former postdoctoral fellow in Fuchs’ lab, noticed something odd in the skin cells just before they turn into squames: darkly-stained protein deposits resembling the droplets you would see if you poured oil into vinegar and gave the mixture a good shake.

This phenomenon, called phase separation, occurs when liquids with mismatched properties come together: The oil prefers to be in the company of other oil, so it separates from the water-based vinegar. Phase separation is also thought to take place inside cells, where the equivalent of oil droplets are poorly understood structures that, unlike many other cellular organelles, are not bound by lipid membranes. Quiroz and his colleagues suspected that in skin cells, the dark protein deposits observed, known as keratohyalin granules, form through phase separation and carry molecular messages that, when released, prompt the cells to quickly flatten and die.

To test this idea directly in skin, Quiroz and his colleagues developed a technique to visualize phase separation dynamics without disrupting a cell’s normal processes. They created mice with a phase separation sensor, a biomolecule that emits green light under the microscope when keratohyalin granules form, and then dissipates when the granules disassemble.

With this method, the researchers were able to show that a protein called filaggrin, which is known to be mutated in some skin conditions, plays a key role in granule formation. “If filaggrin is not functioning properly, phase separation fails to occur, skin lacks keratohyalin granules, and the cells can no longer transform in response to environmental triggers,” says Quiroz.

Barrier breakdown

The findings also shed light on the underlying causes of skin conditions linked to mutations in filaggrin. For example, when Quiroz engineered filaggrin proteins mimicking mutations associated with atopic dermatitis, skin cells could no longer form normal granules. “We suspect that this lack of phase separation contributes to defects in building the skin barrier, resulting in the inflamed, cracked skin that is seen in these conditions,” he says.

Fuchs adds that the work might open up entirely new avenues for developing treatments for this and other filaggrin-linked skin diseases.

“Most treatments developed thus far have been focused on suppressing the immune system, but our findings suggest that we should be looking more closely into the barrier itself,” she says.

Researchers at University of California San Diego School of Medicine have discovered that the enzyme SPRK1 leads the first step in untangling a sperm’s genome, kicking out special packing proteins, which opens up the paternal DNA and allows for major reorganization — all in a matter of hours.

The study published March 12, 2020 in Cell.

“In this study, we were simply interested in answering a fundamental question about the beginning of life,” said senior author Xiang-Dong Fu, PhD, Distinguished Professor in the Department of Cellular and Molecular Medicine at UC San Diego School of Medicine. “But in the process we’ve uncovered a step that might malfunction for some people, and contribute to a couple’s difficulty conceiving. Now that we know SPRK1 plays a role here, its potential part in infertility can be further explored.”

Sperm can be up to 20 times smaller than a normal cell in the body. And while sperm carry only half as much genetic material as a regular cell, it needs to be folded and packaged in a special way in order to fit. One way nature does this is by replacing histones — proteins around which DNA is wound, like beads on a necklace — with a different type of protein called protamines.

Fu’s team has long studied SPRK1 for a completely different reason: its ability to splice RNA, an important step that enables the translation of genes to proteins. They previously showed that SPRK1 is over-activated in colon cancer, and they developed inhibitors to dampen the enzyme.

But back in 1999, shortly after Fu published a paper that first described the enzyme’s role in RNA splicing, a research group in Greece noted similarities in the sequence of amino acid building blocks that make up SPRK1 substrates (the proteins upon which the enzyme acts) and protamine. Fu thought about it for years, but didn’t have the expertise and tools to study sperm development. In 2015, Lan-Tao Gou, PhD, was interviewing for a position as postdoctoral researcher when Fu realized that with Gou’s experience in spermatogenesis, he finally had the right person for the job.

“I said to Lan-Tao, let’s do something nobody else is doing. I have a theory and you have the expertise,” Fu said. “So we borrowed the equipment we needed and leveraged the core facilities we have here at UC San Diego.

“And, surprisingly, everything we tried supported our hypothesis — SRPK1 leads a double life, swapping protamines for histones once sperm meets egg.”

According to Fu, SPRK1 most likely started out playing this role in early embryogenesis, then later evolved the ability to splice RNA. In this way, SPRK1 gets to stick around even when it’s no longer needed for embryogenesis.

Fu, Gou and team next want to determine the signals that instruct sperm to synchronize with the maternal genome.

“We have a ton of new ideas now,” Fu said. “And the better we understand every step in the process of spermatogenesis, fertilization and embryogenesis, the more likely we are to be able to intervene when systems malfunction for couples struggling with reproductive issues.”

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Materials provided by University of California – San Diego. Original written by Heather Buschman, PhD. Note: Content may be edited for style and length.