The structural basis for SARM1 inhibition and activation under energetic stress

This is the author accepted manuscript. The final version is available on open access from eLife Sciences Publications via the DOI in this recordSARM1 an executor of axonal degeneration, displays NADase activity that depletes the key cellular metabolite, NAD+, in response to nerve injury. The basis of SARM1 inhibition, and its activation under stress conditions are still unknown. Here, we present cryo-EM maps of SARM1 at 2.9 and 2.7 Å resolution. These indicate that SARM1 homo-octamer avoids premature activation by assuming a packed conformation, with ordered inner and peripheral rings, that prevents dimerization and activation of the catalytic domains. This inactive conformation is stabilized by binding of SARM1's own substrate NAD+ in an allosteric location, away from the catalytic sites. This model was validated by mutagenesis of the allosteric site, which led to constitutively active SARM1. We propose that the reduction of cellular NAD+ concentration contributes to the disassembly of SARM1's peripheral ring, which allows formation of active NADase domain dimers, thereby further depleting NAD+ to cause an energetic catastrophe and cell death.IS

Prototyp eines elektronischen Nine Hole Peg Tests

Der Nine-Hole-Peg-Test ist ein genormter internationaler Test, der zur Messung der Handgeschicklichkeit dient. Dieser Test wird häufig zur Befundung und/oder Verlaufskontrolle vorwiegend in der Orthopädie und in der Ergotherapie sowie in der Neurologie eingesetzt. Diese vorliegende Arbeit beschäftigt sich mit der Entwicklung eines auf dem klassischen Nine-Hole-Peg-Test basierten elektronischen Prototyps, welcher den physikalischen Nine-Hole-Peg-Test in Embedded Reality bringt, um möglichst viele physikalische Fehler zu minimieren, welche vom Patienten oder vom Spezialisten verursacht werden und die Messergebnisse beeinflussen. Mit einem praktischen und modernen Gehäuseentwurf sowie einer freundlich gestalteten Benutzeroberfläche bietet dieser entwickelte, elektronische Prototyp neben einer präzisen Zeitmessung und einer intelligenten automatischen Auswertungseinheit, ein motivierendes Trainingsspiel mit zwei unterschiedlichen Stufen an, welches dazu dient, die Hände der PatientInnen zu trainieren.The Nine-Hole-Peg-Test is a standardized international test that is used to measure manual dexterity. This test is often used for diagnosis and/or follow-up, mainly in orthopaedics and occupational therapy as well as in neurology. This present paper deals with the development of an electronic prototype based on the classical nine-hole peg test, which brings the physical nine-hole peg test into embedded reality in order to minimize as many physical errors as possible, which are caused by the patient or the specialist and which influence the measurement results. With a practical and modern case design as well as a friendly designed user interface, this developed electronic prototype offers not only precise timing and an intelligent automatic assessment unit, but also a motivating training game with two different levels to train the patients' hands

Prototyp eines elektronischen Nine Hole Peg Test

Der Nine-Hole-Peg-Test begleitet Ergotherapeuten bereits seit vielen Jahren weltweit vorwiegend in der Orthopädie und in der Neurologie. Dieser Test ist international genormt und dient zur Messung der Handgeschicklichkeit und wird häufig zur Befundung und / oder Verlaufskontrolle in der Ergotherapie eingesetzt. Die vorliegende Arbeit beschäftigt sich mit der Entwicklung eines elektronischen auf dem Mikrocontroller STM32F411VE basierten Prototyps. Dieser Prototyp ist auf dem klassischen Nine-Hole-Peg-Test-Gerät aufgebaut. Der entwickelte Prototyp bietet gegenüber dem klassischen Nine-Hole-Peg-Test-Gerät eine präzise Zeitmessung und die automatische Erkennung jedes gültigen durchgeführten Durchlaufs sowie eine freundlich gestaltete Benutzeroberfläche. Die von Patienten durchgeführten Testwerte können einfach auf einer SD-Karte gespeichert werden und jederzeit abgerufen werden.The Nine-Hole-Peg-Test has been used by occupational therapists worldwide for many years, mainly in orthopaedics and neurology. This test is internationally standardised and is used to measure manual dexterity and for diagnosis and/or follow-up in occupational therapy. This thesis deals with the development of an electronic prototype based on the STM32F411VE microcontroller. This prototype is based on the classical Nine-Hole-Peg-Test device. Compared to the classical Nine-Hole-Peg-Test-device the developed prototype offers a precise time measurement and the automatic recognition of each valid performed run as well as a friendly designed user interface. The test values performed by patients can easily be stored on an SD card and can be accessed at any time

Structure-function analysis of ceTIR-1/hSARM1 explains the lack of Wallerian axonal degeneration in C. elegans

Summary: Wallerian axonal degeneration (WD) does not occur in the nematode C. elegans, in contrast to other model animals. However, WD depends on the NADase activity of SARM1, a protein that is also expressed in C. elegans (ceSARM/ceTIR-1). We hypothesized that differences in SARM between species might exist and account for the divergence in WD. We first show that expression of the human (h)SARM1, but not ceTIR-1, in C. elegans neurons is sufficient to confer axon degeneration after nerve injury. Next, we determined the cryoelectron microscopy structure of ceTIR-1 and found that, unlike hSARM1, which exists as an auto-inhibited ring octamer, ceTIR-1 forms a readily active 9-mer. Enzymatically, the NADase activity of ceTIR-1 is substantially weaker (10-fold higher Km) than that of hSARM1, and even when fully active, it falls short of consuming all cellular NAD+. Our experiments provide insight into the molecular mechanisms and evolution of SARM orthologs and WD across species