One particularly vital regulator of dynein is a protein called Lis1. Lis1’s partnership with dynein is essential for proper motor activity, and defects in Lis1 are known to cause lissencephaly, a rare but devastating brain development disorder commonly referred to as “smooth brain” due to its characteristic lack of normal brain folds. Despite the critical nature of this partnership, many aspects of how Lis1 activates dynein and modulates its function have remained mysterious. Now, groundbreaking research led by teams from the Salk Institute and the University of California, San Diego, has captured for the first time short, high-resolution movies revealing the stepwise activation of dynein by Lis1. These movies illustrate sixteen distinct structural conformations of dynein during its interaction with Lis1, providing unprecedented insight into the molecular dance that governs this essential cellular process.

At the molecular level, dynein is a large protein complex composed of two symmetrical halves. Each half includes a stalk domain, which binds to the microtubule; a tail domain, which attaches to the cargo; and a motor domain, which hydrolyzes ATP to generate movement. This ATP-driven motor domain functions somewhat like a biological engine, allowing dynein to “walk” along microtubule tracks. In its inactive state, dynein adopts a locked conformation known as the Phi state, in which it is unable to interact productively with the microtubule, effectively putting the motor “on pause” until activation signals prompt it otherwise.

Prior research had suggested that Lis1 plays the role of an activator or “key” that unlocks dynein, transforming it into an open, active conformation termed the Chi state. However, these conclusions were largely based on static images that captured only snapshots of the dynein-Lis1 interaction at isolated moments, leaving the full dynamic process poorly understood. The new study overcame this limitation by employing time-resolved cryogenic electron microscopy (cryo-EM), a cutting-edge imaging technique that collects a series of structural data points over fractions of a second to generate detailed 3D “movies” of molecular interactions.

Using yeast cells as a model system—chosen for their ability to withstand alterations in dynein and Lis1 levels and the high degree of conservation between yeast and human dynein—the researchers were able to isolate the dynein-Lis1 complex and dramatically lower the temperature to slow the protein motions. This approach made it possible to capture a series of high-definition 3D snapshots that, when combined, depict a continuous timeline from dynein’s locked Phi state through a series of intermediates to the fully activated Chi conformation.

The findings reveal a sophisticated, multi-step activation mechanism. In the first step, one half of the Lis1 dimer binds to the motor domain of dynein. This initial contact disrupts dynein’s locked conformation, “turning on” the motor by prompting a shape change that enhances ATP hydrolysis efficiency and primes the protein for movement. Subsequently, the second half of Lis1 binds to the stalk domain of dynein, further stabilizing the activated conformation and significantly boosting dynein’s motor activity. This two-tiered interaction not only unlocks dynein but also amplifies its capacity to harness ATP energy for rapid and directed transport along the microtubules.

The biological implications of these discoveries extend far beyond the realm of basic cellular biology. Lis1-associated dynein dysfunction is critical in the etiology of lissencephaly and other neurological disorders, which currently have no cure. By deciphering the precise molecular details of dynein activation, this research lays a foundation for rational drug design aimed at restoring proper motor function. For example, small molecules engineered to emulate Lis1’s activating effects on dynein could potentially counteract the impacts of Lis1 mutations or deficiencies.

Furthermore, the high-resolution cryo-EM data give researchers a detailed roadmap of potential binding sites for therapeutic compounds within the dynein-Lis1 complex. Mapping these targetable sites opens new avenues to develop precision medicines that modulate motor protein activity at the atomic level, providing hope for treating not only rare genetic brain disorders but potentially a broader range of neurodegenerative diseases where cellular transport pathways are compromised.

Looking forward, further investigations will focus on dissecting how specific mutations in Lis1 or dynein contribute to disease states by altering their interaction dynamics. Moreover, expanding these studies to human proteins and neuronal cell models will be critical in validating the therapeutic potential suggested by the yeast model findings. These efforts signify an important step toward bridging molecular insights with clinical applications.

This study exemplifies the power of advanced structural biology techniques like time-resolved cryo-EM in transforming our understanding of dynamic protein machines. By transforming still images into molecular movies, researchers can now witness the intricate choreography that underlies fundamental processes such as intracellular transport. The capacity to visualize molecular events as they unfold in near real-time will undoubtedly accelerate the discovery of novel treatments for complex diseases linked to protein dysfunction.

The research was conducted by a collaborative team including Agnieszka Kendrick of the Salk Institute, Andres Leschziner of UC San Diego, and colleagues such as Kendrick Nguyen, Eva Karasmanis, Rommie Amaro, Samara Reck-Peterson, and Wen Ma. Supported by prestigious funding bodies including the American Cancer Society, National Institutes of Health, the Cardiovascular Research Institute of Vermont, Jane Coffin Childs Postdoctoral Fellowship, and the Howard Hughes Medical Institute, this work underscores the importance of interdisciplinary collaboration in pushing the frontiers of biomedical science.

As a distinguished institution, the Salk Institute continues to advance the understanding of life’s most intricate mechanisms, from neuroscience to cancer, aging, and beyond. Founded by Jonas Salk, the architect of the first safe polio vaccine, the Institute embodies a legacy of dedication to uncovering biological truths with the potential to transform human health.

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Subject of Research: Molecular mechanisms of dynein motor protein activation by Lis1 and implications for neurodevelopmental disorders.

Article Title: Multiple steps of dynein activation by Lis1 visualized by cryo-EM.

News Publication Date: May 23, 2025.

Web References: https://www.nature.com/articles/s41594-025-01558-w

References: Kendrick A., Leschziner A., et al. (2025). Multiple steps of dynein activation by Lis1 visualized by cryo-EM. Nature Structural & Molecular Biology. DOI: 10.1038/s41594-025-01558-w

Image Credits: Agnieszka Kendrick, Salk Institute

Keywords: Dynein, Lis1, motor proteins, microtubules, cryo-electron microscopy, neurodevelopmental disorders, lissencephaly, protein activation, intracellular transport, structural biology, ATP hydrolysis, neurodegeneration

Mitochondria, often described as the powerhouses of the cell, are essential organelles responsible for converting nutrients into adenosine triphosphate (ATP), the molecule that powers virtually all biological activities. Muscle tissues, known for their high energy demands, rely heavily on the proper functioning of mitochondria to sustain movement and endurance. However, mitochondrial dysfunction is a hallmark of numerous metabolic and neuromuscular disorders, including muscular dystrophy, multiple sclerosis, and age-related decline, posing a significant challenge for effective medical intervention.

The Salk team’s work delves deep into the molecular biology governing mitochondrial biogenesis — the process by which cells generate new mitochondria, especially in response to increased energy demands such as exercise. Central to this process are estrogen-related receptors (ERRs), members of the nuclear hormone receptor family, which regulate gene expression by binding directly to DNA. Unlike their classical counterparts, the functions of ERRs had remained largely elusive since their discovery in the late 1980s.

Through meticulous experimentation involving genetically engineered mouse models lacking various ERR isoforms — alpha, beta, and gamma — the researchers observed striking effects on mitochondrial quantity and functionality in muscle cells. Notably, deletion of ERRα alone produced mild changes due to compensation by the gamma isoform, which, although only constituting around 4% of the ERR population, exhibited a crucial compensatory role under resting conditions. Simultaneous elimination of both ERRα and ERRγ, however, precipitated severe mitochondrial abnormalities, underscoring their cooperative necessity in sustaining muscle metabolic capacity.

These findings suggest an evolutionary design wherein ERRα’s abundance primes muscles for rapid adaptation and growth in energy production in response to physiological stimuli. Indeed, when mice lacking ERRα were subjected to exercise regimes using mechanical running wheels, mitochondrial biogenesis — normally induced by physical activity — was completely blocked. This pivotal experiment illuminates the indispensable role of ERRα in enabling muscles to meet heightened energy demands, effectively acting as a gatekeeper of exercise-induced mitochondrial proliferation.

Historically, the protein PGC1α has been recognized as a master regulator of mitochondria across multiple tissues. Nonetheless, its therapeutic appeal is limited by its indirect interaction with DNA, necessitating partnership with nuclear receptors like ERRα to modulate gene transcription. The Salk study substantiates that ERRα directly binds to mitochondrial energy metabolism genes and synergizes with PGC1α to orchestrate the robust genomic response required for mitochondrial biogenesis during exercise.

The implications of these mechanistic insights are profound. By targeting ERRs, particularly ERRα, it may be possible to pharmacologically stimulate mitochondrial growth and enhance metabolic efficiency in individuals incapable of engaging in physical activity due to muscle weakness or chronic illness. Such interventions could ameliorate symptoms of metabolic dysfunction and muscle fatigue prevalent in a broad spectrum of disorders, including muscular dystrophies, aging-related sarcopenia, and systemic metabolic syndromes.

Moreover, ERRs’ expression in vital organs such as the heart and brain extends the therapeutic horizon beyond skeletal muscle. By potentiating mitochondrial energetics in these tissues, drugs designed to activate estrogen-related receptors might confer systemic benefits, potentially improving cardiovascular health and cognitive function through enhanced cellular bioenergetics.

This research represents a significant advance in understanding the transcriptional regulation of mitochondrial biogenesis and the intricate cellular pathways that sustain energy homeostasis. With estrogen-related receptors functioning as pivotal modulators, the door opens to innovative drug discovery programs focused on ERR agonists or modulators, heralding a new era in the management of metabolic and neuromuscular diseases.

Future investigations are warranted to unravel the precise regulatory networks between ERR isoforms and their interactions with co-regulators like PGC1α, as well as to explore the safety and efficacy of potential ERR-targeting compounds in clinical settings. Furthermore, elucidating the nuances of ERR regulation in various tissue contexts will be paramount to designing tailored therapeutics that maximize benefit and minimize adverse effects.

In synthesizing these findings, it becomes evident that the metabolic resilience of muscle and other high-energy organs hinges critically on the robust function of estrogen-related receptors. Their strategic activation could emulate the physiological benefits of exercise at the molecular level, offering hope for patients burdened by metabolic insufficiencies and expanding the arsenal against diseases rooted in mitochondrial dysfunction.

This seminal research, published in the prestigious Proceedings of the National Academy of Sciences on May 12, 2025, underscores the enduring importance of fundamental molecular biology in unveiling therapeutic targets with far-reaching clinical ramifications. As the Salk Institute continues to push the frontiers of knowledge, the scientific community eagerly anticipates the translation of these insights into tangible treatments that invigorate mitochondrial health and revitalize muscle function across diverse populations.

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Subject of Research: Muscle mitochondrial energetics and estrogen-related receptor regulation
Article Title: Estrogen-related receptors regulate innate and adaptive muscle mitochondrial energetics through cooperative and distinct actions
News Publication Date: May 16, 2025
Web References: https://doi.org/10.1073/pnas.2426179122
Image Credits: Salk Institute
Keywords: Life sciences, Cell biology, Cellular physiology, Cell metabolism, Cellular energy, Animal cells, Muscle cells, Mitochondrial diseases, Metabolic disorders, Muscle diseases, Movement disorders, Mitochondria, Cell structure

The findings emerge in a healthcare landscape still reeling from the impacts of the COVID-19 pandemic, where a surge of interest in understanding the interplay between mental health treatments and immune response has been observed. Notably, previous studies have indicated that SSRI users experienced less severe COVID-19 infections and demonstrated lower rates of long COVID symptoms. The Salk research builds upon this foundation, shifting paradigms about the potential utility of fluoxetine, the active ingredient in Prozac, not only in psychiatric care but also in infectious disease treatment.

In their study published in the prestigious journal Science Advances, the researchers conducted experiments on mice with bacterial infections, employing a systematic approach to investigate the drug’s efficacy. They segregated the subjects into two groups: one pretreated with fluoxetine and the other receiving standard healthcare. The experimental outcomes were pronounced; mice that had received fluoxetine showcased a significant reduction in the severity of infections, pointing to the drug’s antimicrobial properties as a pivotal discovery.

From the onset of infection, researchers measured bacterial counts in both cohorts. Remarkably, the fluoxetine-treated mice harbored fewer bacteria compared to their untreated counterparts, suggesting that the drug actively contributes to limiting bacterial proliferation. This novel antimicrobial action significantly implicates fluoxetine in potentially redefining infection management strategies, particularly in the context of sepsis, which poses acute risks to human health through exaggerated immune responses leading to tissue damage and organ failure.

The Salk team delved deeper into the physiological mechanisms at play by examining inflammatory markers within the infected subjects. A particular focus was given to interleukin-10 (IL-10), an anti-inflammatory cytokine whose elevated levels in the fluoxetine-treated group demonstrated clear linkage to improved metabolic control during infection episodes. This revelation aligns with the understanding that each infection could be countered not merely by antimicrobial activity, but also through modulatory effects that restrain the body’s damaging inflammatory responses.

A key takeaway from the research highlights that fluoxetine’s protective roles appear independent of its interactions with serotonin—a neurotransmitter often associated with mood regulation that SSRIs typically influence. When the study introduced two additional sets of mice, segregating them based on the presence or absence of circulating serotonin, the results garnered attention. Both groups exhibited equivalent protective benefits from fluoxetine, challenging pre-existing assumptions about the neuro-pharmacological basis of these drugs and refocusing attention on their immunological capabilities.

Professor Janelle Ayres, the study’s lead author and a distinguished researcher at the Salk Institute, expressed enthusiasm about these unanticipated findings. The prospect of utilizing an extensively researched and widely prescribed medication like fluoxetine for enhancing immune response is a groundbreaking achievement with the potential to revolutionize infection treatment paradigms. The ability of a single medication to exert both antimicrobial effects alongside tissue protection exemplifies an innovative approach to combating diseases linked to immune dysregulation.

In a clinical context, these findings could reshape therapeutic strategies not only for sepsis but also for chronic conditions where the immune response is dysregulated. This dual-functionality of fluoxetine sparks interest towards investigating other SSRIs for comparative efficacies in infection prevention and treatment. As the researchers emphasize, fluoxetine represents a unique opportunity where a drug’s safety profile for mental health use can drive advancement in standards and practices for critical illness management, particularly in an era where re-purposed medications are gaining traction.

Future research endeavors will further examine the appropriate dosing regimens of fluoxetine in septic patients, with an emphasis on timing and administration to maximize therapeutic efficacy while minimizing risks. Understanding the dynamics of fluoxetine in clinical settings could open new pathways in managing infections, especially in vulnerable populations who are at heightened risk of developing severe complications.

As the narratives surrounding depression and anxiety evolve alongside discussions on immunity and infection, the implications of these findings resonate deeply across clinical, psychological, and public health domains. Reinventing the narrative of antidepressants, this research not only highlights their value in mental health but also positions them as potential allies in the face of infectious diseases, ultimately aiming to foster a more resilient healthcare framework.

The dialogue surrounding the Salk research emphasizes the necessity of integrating mental health disciplines and infectious disease studies, advocating for collaborative approaches in future research. As scientists and clinicians unite to unravel the complexities of human health, embracing emerging insights from both fields may pave the way toward more comprehensive treatment solutions that encompass the interconnectedness of our biological systems.

Ultimately, the revelations made by this research might stimulate further explorations into pharmaceuticals that could serve multifunctional roles. The scientific community is eager to see how the exploration of fluoxetine’s immunomodulatory capabilities progresses, paving the path for a future where mental health medications are transformed into critical components of holistic health care strategies.

This paradigm shift may also encourage a broader acceptance of SSRIs as a potentially vital tool in combatting not only psychological disorders but infectious processes as well, providing a foundation for continuous advancement in therapeutic interventions that prioritize dual actions within the body to achieve optimal health outcomes.

In conclusion, as the world navigates the challenges of infectious diseases along with mental health concerns, these novel findings invite scrutiny and admiration alike, marking a significant milestone in the quest for knowledge that bridges the gap between mind and body, with implications that hold promise for both current and future generations.

Subject of Research: The dual role of fluoxetine (Prozac) as a modulator of immune response against infections and sepsis.
Article Title: Fluoxetine promotes IL-10 dependent metabolic defenses to protect from sepsis-induced lethality
News Publication Date: February 14, 2025
Web References: Salk Institute
References: DOI Link
Image Credits: Salk Institute

Keywords: Antidepressants, fluoxetine, sepsis, immune response, antimicrobial properties, SSRIs, metabolic defense, inflammation, COVID-19, mental health, infection management, IL-10.