Cofilin1 oxidation links oxidative distress to mitochondrial demise and neuronal cell death

Many cell death pathways, including apoptosis, regulated necrosis, and ferroptosis, are relevant for neuronal cell death and share common mechanisms such as the formation of reactive oxygen species (ROS) and mitochondrial damage. Here, we present the role of the actin-regulating protein cofilin1 in regulating mitochondrial pathways in oxidative neuronal death. Cofilin1 deletion in neuronal HT22 cells exerted increased mitochondrial resilience, assessed by quantification of mitochondrial ROS production, mitochondrial membrane potential, and ATP levels. Further, cofilin1-deficient cells met their energy demand through enhanced glycolysis, whereas control cells were metabolically impaired when challenged by ferroptosis. Further, cofilin1 was confirmed as a key player in glutamate-mediated excitotoxicity and associated mitochondrial damage in primary cortical neurons. Using isolated mitochondria and recombinant cofilin1, we provide a further link to toxicity-related mitochondrial impairment mediated by oxidized cofilin1. Our data revealed that the detrimental impact of cofilin1 on mitochondria depends on the oxidation of cysteine residues at positions 139 and 147. Overall, our findings show that cofilin1 acts as a redox sensor in oxidative cell death pathways of ferroptosis, and also promotes glutamate excitotoxicity. Protective effects by cofilin1 inhibition are particularly attributed to preserved mitochondrial integrity and function. Thus, interfering with the oxidation and pathological activation of cofilin1 may offer an effective therapeutic strategy in neurodegenerative diseases.Subject terms: Apoptosis, Cell death in the nervous system, Neurodegeneration     

Structural constraints from residual tensorial couplings in high resolution NMR without an explicit term for the alignment tensor

Structural restraints from residual tensorial couplings in high resolution NMR are usually incorporated into molecular structure calculation programs by an energy penalty function which depends on the knowledge of the alignment tensor. Here, we show that the alignment tensor enters in linear form into such a function. Therefore, the explicit appearance of the alignment tensor can be eliminated from the penalty function. This avoids the necessity of a determination of magnitude and rhombicity of the alignment tensor in the absence of structural information. The price for this procedure is a slightly shallower energy landscape. Simulations in the vicinity of the energy minimum for the backbone of human ubiquitin show that the reduction in curvature is on the order of a few percent.     

Load-dependent kinetics of myosin-V can explain its high processivity

Recent studies provide strong evidence that single myosin class V molecules transport vesicles and organelles processively along F-actin, taking several 36-nm steps, 'hand over hand', for each diffusional encounter. The mechanisms regulating myosin-V's processivity remain unknown. Here, we have used an optical-tweezers-based transducer to measure the effect of load on the mechanical interactions between rabbit skeletal F-actin and a single head of mouse brain myosin-V, which produces its working stroke in two phases. We found that the lifetimes of the first phase of the working stroke changed exponentially and about 10-fold over a range of pushing and pulling forces of +/- 1.5 pN. Stiffness measurements suggest that intramolecular forces could approach 3.6 pN when both heads are bound to F-actin, in which case extrapolation would predict the detachment kinetics of the front head to slow down 50-fold and the kinetics of the rear head to accelerate respectively. This synchronizing effect on the chemo-mechanical cycles of the heads increases the probability of the trail head detaching first and causes a strong increase in the number of forward steps per diffusional encounter over a system with no strain dependence.     

Effects of resource distribution, patch spacing, and preharvest information on foraging decisions of northern bobwhites

We investigated patch assessment by northern bobwhites (Collinusvirginianus) in an experimental arena where the distributionof resources in patches, preharvest information about thesepatches, and spacing of patches varied. We found that preharvestinformation about patch quality and a bimodal distribution ofpatch rewards allowed birds to selectively exploit patches highin resources. In contrast, uniform distribution of patch qualitiesand lack of preharvest information caused birds to forage nonselectivelyamong patches. Birds distinguished among patches of differentquality when these patches were spaced 13 m apart, but failedto react to patch quality differences when patches were 0 or3 m apart We also found a strong effect of the level of patchdepletion on foraging decisions: as resources in die arena becamescarce, birds increasingly foraged selectively in die most profitablepatches. Foraging decisions of bobwhites are biased by die waythey experience and memorize a spatially and temporally variableenvironment. The relative cost of this cognitive bias (i.e.,lost opportunity) is nonlinearty related to die mean resourcedensity in die environment and to die difference between thismean density and die resource density in die exploited patch.Cognitive bias should be considered when evaluating patch assessmentcapabilities of foragers in complex environments.     

Chirality of peptide bond-forming condensation domains in nonribosomal peptide synthetases: the C5 domain of tyrocidine synthetase is a (D)C(L) catalyst

Nonribosomal peptides (NRP) such as the antibiotic tyrocidine have D-amino acids, introduced by epimerase (E) domains embedded within modules of the enzymatic assembly lines. We predict that the peptide bond-forming condensation (C) domains immediately downstream of E domains are D-specific for the peptidyl donor and L-specific for the aminoacyl acceptor ((D)C(L)). To validate this prediction and establish that the C(5) domain of tyrocidine synthetase is indeed (D)C(L), the apoT (thiolation) forms of module 4 (TycB(3) AT(4)E) and module 5 (TycC(1) C(5)AT(5)) were expressed. T(5) was posttranslationally primed with CoASH to introduce the HS-pantetheinyl group and autoaminoacylated with radiolabeled L-Asn* or L-Asp*. Alternate donor substrates were introduced by priming apo AT(4)E with synthetically prepared tetrapeptidyl-CoA's differing in the chirality of Phe-4, D-Phe-L-Pro-L-Phe-L-Phe-CoA, and D-Phe-L-Pro-L-Phe-D-Phe-CoA. The tetrapeptidyl-S-T(4) and L-Asp-S-T(5) were studied for peptide bond formation and chain translocation by C(5) to yield pentapeptidyl-S-T(5), whose chirality (D-L-L-D-L- vs D-L-L-L-L-) was assayed by thioester cleavage and chiral chromatography of the released pentapeptides. Only the D-Phe-4 pentapeptidyl-S-T(5) was generated, implying that only D-L-L-D-S-T(4) was utilized, proving C(5) is indeed a (D)C(L) catalyst. Furthermore, a mutant with an inactive E domain transferred tetrapeptide only when loaded with D-Phe-4 tetrapeptidyl donor, not L-Phe-4, confirming that in the wild-type assembly line C(5) only transfers D-L-L-L-tetrapeptidyl-S-T(4) after in situ epimerization by the E domain. These results contrast the observation that C(5) can make both L-Phe-L-Asn and D-Phe-L-Asn when assayed with Phe as the donor substrate. Hence, utilizing an aminoacyl-S-T(4) versus the natural peptidyl-S-T(4) donor produced misleading information regarding the specificity of the condensation domain.