HAT

Biophysicists have gained a new insight about the dynamics of cellular movement, which is key to processes ranging from stem-cell differentiation and wound healing to the development of diseases such as cancer. A single human cell teems with as many 100,000 different proteins. Actin is one of the most abundant and essential of them all. This protein forms into filaments that help make up the skeleton of cells, giving them shape. And as the actin filaments elongate, they work like muscles, pushing against the inner membrane of a cell to move it forward. Three other proteins are known to drive the activities of actin. One class of protein assembles individual actin molecules into actin filaments, another causes the filaments to stop growing and a third disassembles filaments. Biophysicists at Emory University, however, have discovered an even more complex and nuanced view of how these three proteins together influence actin dynamics. Nature Communications published the findings, showing how these proteins sometimes shift from solo or duet acts to perform as a trio, allowing them to fine-tune the activity of actin filaments. The discovery opens another window onto the dynamics of cellular movement, which is key to processes ranging from stem-cell differentiation and wound healing to the development of diseases such as cancer. "We found that while these three proteins do one thing when working on their own, they do a completely different thing when the other two proteins join them," says Shashank Shekhar, Emory assistant professor of physics and cell biology, and senior author of the study. "It gets really complex, very fast." "No one had looked at all of these proteins interacting at once on actin," adds Heidi Ulrichs, co-first author of the study and an Emory PhD candidate in biochemistry, cell and developmental biology. "Our paper is the first report of all three of them occupying the same barbed end of an actin filament." Ulrichs worked closely on the project with Ignas Gaska, a postdoctoral fellow in the Shekkhar lab who is co-first author of the paper. Research into how proteins act individually on actin is relatively well-characterized. A polymerase protein, such as formin, drives elongation of actin. Formin positions itself at the end of an actin filament, grabs onto free-floating actin molecules and stacks them up one by one to keep growing the end. Depolymerase proteins, such as twinfilin, are another class of proteins that influence actin. Twinfilin works like a lint roller, binding to the end of a filament and peeling away one molecule at a time. Twinfilin can repeat the process to disassemble the actin filament entirely. Proteins known as cappers can stop the elongation and disassembling of the filaments. A capper attaches to the end of an actin filament and covers it like a hat, blocking activity by the other proteins. This knowledge was built up by isolating one protein at a time to study how it influences actin. More recent studies have also shown simultaneous interactions between twinfilin and capping proteins. For the current study, the researchers wanted to explore whether formin, twinfilin and the capping protein could all three act simultaneously on actin. "An actin filament end is really tiny, just five nanometers across," Shekhar explains. "One thought was that there just isn't enough real estate available for three proteins to work on a single actin filament at once." The Shekhar Lab is one of only a handful in the world using the highly specialized technique of microfluidics-assisted total internal reflection fluorescence microscopy (mf-TIRF) to study how the actin cytoskeleton remodels itself. Cells are packed with thousands of proteins moving around, performing different functions, making it impossible to track all of them. Researchers must isolate the proteins of interest and study them outside of a cellular system, by introducing them to a microfluidic system on a microscope slide. The mf-TIRF technology allows the Shekhar Lab to attach fluorescent orbs to single protein molecules so that researchers can better observe what these molecules are doing through a microscope. In experiments, the researchers tagged molecules of actin, formin, twinfilin and the capping protein with four different colors that emitted fluorescent light. They then introduced actin to the microfluidic system and added the other proteins one at a time. The results startled them. When twinfilin, the protein that breaks apart an actin filament, was added in the presence of both formin and the capping protein, twinfilin actually worked to speed up the process of filament elongation. "That's counterintuitive, which is cool," Ulrichs says. "Doing science you get surprised all the time." Twinfilin alone could not join formin on the end of the actin filament. However, when the capping protein was also present, all three could simultaneously work together on the tiny surface of the actin filament. Shekhar compares the effects of all three proteins working together to a knob that allows for more precise control of a process. "Our findings establish a new paradigm in which the three proteins work in concert to fine-tune how fast or slowly actin filaments are formed," he says. The dynamics of how the three proteins interact with actin is fundamental to teasing apart the complex mysteries of how cells function normally and what happens when something goes wrong. "We're building up knowledge, step by step, study by study, on the dynamics of what's happening inside of a cell," Ulrichs says.

News on COVID-19 vaccine developments and disease studies continue to deliver highs and lows. Here are some of the more recent happenings. Pfizer-BioNTech Vaccine Demonstrates 100% Efficacy for 12-15 Age Group Pfizer said its COVID-19 vaccine, developed with BioNTech, demonstrated 100% effectiveness in the 12 to 15-year-old age group after four months. Data collected from November 2020 to September 2021 from participants who received two doses of the vaccine (at 30-µg per dose) showed total efficacy across gender, race and ethnicity demographics, comorbidity, and obesity status. The participants were observed seven days after their second dose and in the over four months that followed. Any adverse events seen were consistent with the drug's clinical safety data, and no serious safety issues arose. "These are the first and only disclosed longer-term data demonstrating the safety and efficacy of a COVID-19 vaccine in individuals 12 to 15 years of age. The growing body of data we have compiled from clinical trials and real-world surveillance to date strengthen the base of evidence supporting the strong efficacy and favorable safety pro our COVID-19 vaccine across adolescent and adult populations," said Ugur Sahin, chief executive officer and co-founder of BioNTech, in a statement. Findings from this latest study will strengthen the planned application for the supplemental Biologics License Application (sBLA) to be submitted to the U.S. Food and Drug Administration (FDA). So far, the Pfizer-BioNTech vaccine is available for the 12 to 15-year-old age group under emergency use authorization (EUA), which was granted in May 2021. SyneuRx Anti-viral Drug Candidate Prepares to Go Into Phase III Trial SyneuRx International, the pharmaceutical firm focused on anti-viral and central nervous system drugs, announced that its oral SARS-CoV-2 anti-viral candidate is ready to go into Phase III trial after a successful seven-month Phase II run. Pentarlandir has botanical origins and is based on highly purified isomers of tannic acid. It works by targeting the main protease, 3CL-protease, which turns viral protein into the necessary components that enable the replication of new viral particles that help inhibit TMPRSS2 and HAT for viral entry. This dual function makes it a good candidate for so-called "twindemic" situations as it can address both COVID-19 and influenza. Pentarlandir is given orally to patients suffering from breakthrough cases of the virus (among those who had been previously infected or vaccinated). It is also indicated as a possible first-line treatment for those who are unvaccinated and might face hospitalization or death. "Our researchers have devoted several years to the discovery, isolation and development of Pentarlandir and we are very pleased with the progress of the Phase II trial. We are actively developing this candidate drug and remain hopeful that we will continue our positive track record to date," commented Guochuan 'Emil' Tsai, M.D., Ph.D., MAS, the founder and CEO of SyneuRx. The drug is expected to be widely available worldwide within one to two years after the Phase III study is completed. Pregnant Women With COVID-19 At Risk for Stillbirths A new study by scientists from the Centers for Disease Control and Prevention (CDC) has shown that pregnant women diagnosed with COVID-19 are at increased risk for stillbirth compared to those without the virus. The danger is even higher if the woman is carrying the Delta variant. Based on information collected from the Premier Healthcare Database Special COVID-19 Release (PHD-SR), a large U.S. hospital-based administrative database, the CDC observed that many of the stillbirths recorded from March 2020 to June 2021 and July to September 2021 were of women who had COVID-19 at the time of delivery. Many of the cases were also strongly linked during the predominance of the Delta variant. "Although stillbirth was a rare outcome overall, a COVID-19 diagnosis documented during the delivery hospitalization was associated with an increased risk for stillbirth in the United States, with a stronger association during the period of Delta variant predominance. Among deliveries with COVID-19 documented during the delivery hospitalization, certain underlying medical conditions and markers of maternal morbidity, including the need for intensive care, were associated with stillbirth. Additional studies are warranted to investigate the role of maternal complications from COVID-19 on the risk for stillbirth," noted the CDC research. Although the CDC admitted several limitations to its research, including lack of laboratory details and reliance on data from hospital discharge alone, the findings add to the growing evidence between COVID-19 in pregnancy and maternal conditions. The CDC said that this highlights the need for further investigation into treatment and prevention strategies. FDA Says Access to its Full Vaccine Records OK, But Wait ‘Til 2076 The FDA this week said that it could take over 55 years for the agency to review and release a complete report on the vaccine-related documentation it currently holds in response to a lawsuit filed by scientists demanding to see the complete records. A group of over 30 professors and scientists from different universities filed a lawsuit in September with the U.S. District Court for the Northern District of Texas seeking expedited access to the FDA's vaccine According to the filing, the call for transparency is meant to assuage skepticism over the safety and effectiveness of the Pfizer vaccine, which the FDA has supported for almost all age groups and demographics. However, in a joint status report dated November 22, the FDA and the Department of Justice said that it's not easy to turn over the wholesale documents. Each be reviewed thoroughly to redact any confidential details and trade secrets that might leak if the process is rushed. The FDA proposed to release 500 pages per month on a rolling basis, not only because they only have 10-person team capable of getting it done, but also because this same team is processing around 400 other similar FOIA requests. As of this writing, the FDA assessed that there are over 329,000 pages that could fulfill the group's request. "As should be apparent, the review conducted by FDA scientists when considering to approve a product is entirely different from the review conducted by FDA government information specialists when considering whether FDA must keep certain information confidential. Moreover, FDA’s FOIA office does not have nearly the same level of personnel or resources dedicated to process FOIA requests as FDA has marshaled to review license applications for life-saving products in the middle of a pandemic," said the statement. The plaintiffs have requested the Court to require the FDA to produce all documents on or before March 3, 2022. "The FDA should welcome making these documents available to the Plaintiff if it is confident in the analysis and review it conducted. The fact that it has fought tooth and nail and taken such an absurd and unconscionable position of waiting until the year 2076 to complete the production further heightens the grave need to have these documents produced forthwith. To require less (than 108 days) is to render FOIA meaningless, the FDA’s promise of transparency a lie," said the plaintiffs.