Arabidopsis katanin binds microtubules using a multimeric microtubule-binding domain.

Katanin is a heterodimeric protein that mediates ATP-dependent destabilization of microtubules in animal cells. In plants, the catalytic subunit of Arabidopsis thaliana katanin (AtKSS, Arabidopsis thaliana Katanin Small Subunit) has been identified and its microtubule-severing activity has been demonstrated in vitro. In vivo, plant katanin plays a role in the organization of cortical microtubules, but the way it achieves this function is unknown. To go further in our understanding of the mechanisms by which katanin severs microtubules, we analyzed the functional domains of Arabidopsis katanin. We characterized the microtubule-binding domain of katanin both in vitro and in vivo. It corresponds to a poorly conserved sequence between plant and animal katanins that is located in the N-terminus of the protein. This domain interacts with cortical microtubules in vivo and has a low affinity for microtubules in vitro. We also observed that katanin microtubule-binding domain oligomerizes into trimers. These results show that, besides being involved in the interaction of katanin with microtubules, the microtubule-binding domain may also participate in the oligomerization of katanin. At the structural level, we observed that AtKSS forms ring-shaped oligomers

Study of supports for the final doublets of ATF2

We investigated supports for the final doublets of ATF2 with vertical relative motion to the floor of final doublets below 10nm. Our calculations of relative motion were done by using data of ATF ground motion. We studied the vibratory behaviour of a steel lightweight honeycomb table as a base for fixing magnets. First, the table was fixed to the floor by four steel feet at its corners. Its first vertical resonance was at 41Hz, which induces a non negligible relative motion (5.7nm) compared to ATF2 tolerances. Modal shape measurements show that the six first resonances of the table (below 150Hz) are rigid body modes in the six degrees of freedom. The conclusion of these measurements is that the table is very rigid and well adapted for ATF2 project but the rigidity of the four steel feet is not sufficient compared to the rigidity of the table. Consequently, the table was fixed to the floor on one entire face to break these six rigid body modes by three large steel plates. The first vertical resonance was then at higher frequencies (92Hz), which show that good boundary conditions were chosen for the table. The relative motion was then low (3.5nm above 0.1Hz) compared to ATF2 tolerances. To finish, we studied the vibratory behaviour of one ATF2 FD sextupole and one ATF2 FD quadrupole with their intermediary supports made at LAPP and used to fix these magnets to the honeycomb table. The measurements showed that the final doublets with their intermediary supports were well designed because the first resonance of sextupoles and quadrupoles was at high frequency (above 100 Hz and at 76Hz respectively), which induced a small relative motion of final doublets to the floor compared to ATF2 tolerances

The Universal One-Loop Effective Action

We present the universal one-loop effective action for all operators of dimension up to six obtained by integrating out massive, non-degenerate multiplets. Our general expression may be applied to loops of heavy fermions or bosons, and has been checked against partial results available in the literature. The broad applicability of this approach simplifies one-loop matching from an ultraviolet model to a lower-energy effective field theory (EFT), a procedure which is now reduced to the evaluation of a combination of matrices in our universal expression, without any loop integrals to evaluate. We illustrate the relationship of our results to the Standard Model (SM) EFT, using as an example the supersymmetric stop and sbottom squark Lagrangian and extracting from our universal expression the Wilson coefficients of dimension-six operators composed of SM fields.Comment: 30 pages, v2 contains additional comments and corrects typos, version accepted for publication in JHE

Continuation vs Discontinuation of Renin-Angiotensin System Inhibitors Before Major Noncardiac Surgery

ImportanceBefore surgery, the best strategy for managing patients who are taking renin-angiotensin system inhibitors (RASIs) (angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) is unknown. The lack of evidence leads to conflicting guidelines.ObjectiveTo evaluate whether a continuation strategy vs a discontinuation strategy of RASIs before major noncardiac surgery results in decreased complications at 28 days after surgery.Design, setting, and participantsRandomized clinical trial that included patients who were being treated with a RASI for at least 3 months and were scheduled to undergo a major noncardiac surgery between January 2018 and April 2023 at 40 hospitals in France.InterventionPatients were randomized to continue use of RASIs (n = 1107) until the day of surgery or to discontinue use of RASIs 48 hours prior to surgery (ie, they would take the last dose 3 days before surgery) (n = 1115).Main outcomes and measuresThe primary outcome was a composite of all-cause mortality and major postoperative complications within 28 days after surgery. The key secondary outcomes were episodes of hypotension during surgery, acute kidney injury, postoperative organ failure, and length of stay in the hospital and intensive care unit during the 28 days after surgery.ResultsOf the 2222 patients (mean age, 67 years [SD, 10 years]; 65% were male), 46% were being treated with angiotensin-converting enzyme inhibitors at baseline and 54% were being treated with angiotensin receptor blockers. The rate of all-cause mortality and major postoperative complications was 22% (245 of 1115 patients) in the RASI discontinuation group and 22% (247 of 1107 patients) in the RASI continuation group (risk ratio, 1.02 [95% CI, 0.87-1.19]; P = .85). Episodes of hypotension during surgery occurred in 41% of the patients in the RASI discontinuation group and in 54% of the patients in the RASI continuation group (risk ratio, 1.31 [95% CI, 1.19-1.44]). There were no other differences in the trial outcomes.Conclusions and relevanceAmong patients who underwent major noncardiac surgery, a continuation strategy of RASIs before surgery was not associated with a higher rate of postoperative complications than a discontinuation strategy.Trial registrationClinicalTrials.gov Identifier: NCT03374449

Functional evidence for in vitro microtubule severing by the plant katanin homologue.

Temporal and spatial assembly of microtubules in plant cells depends mainly on the activity of microtubule-interacting proteins, which either stabilize, destabilize or translocate microtubules. Recent data have revealed that the thale cress (Arabidopsis thaliana) contains a protein related to the p60 catalytic subunit of animal katanin, a microtubule-severing protein. However, effects of the plant p60 on microtubule assembly are not known. We report the first functional evidence that the recombinant A. thaliana p60 katanin subunit, Atp60, binds to microtubules and severs them in an ATP-dependent manner in vitro. ATPase activity of Atp60 is stimulated by low tubulin/katanin ratios, and is inhibited at higher ratios. Considering its properties in vitro, several functions of Atp60 in vivo are discussed