APP controls the formation of PI(3,5)P2 vesicles through its binding of the PIKfyve complex

Phosphoinositides are signalling lipids that are crucial for major signalling events as well as established regulators of membrane trafficking. Control of endosomal sorting and endosomal homeostasis requires phosphatidylinositol-3-phosphate (PI(3)P) and phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2), the latter a lipid of low abundance but significant physiological relevance. PI(3,5)P2 is formed by phosphorylation of PI(3)P by the PIKfyve complex which is crucial for maintaining endosomal homeostasis. Interestingly, loss of PIKfyve function results in dramatic neurodegeneration. Despite the significance of PIKfyve, its regulation is still poorly understood. Here we show that the Amyloid Precursor Protein (APP), a central molecule in Alzheimer’s disease, associates with the PIKfyve complex (consisting of Vac14, PIKfyve and Fig4) and that the APP intracellular domain directly binds purified Vac14. We also show that the closely related APP paralogues, APLP1 and 2 associate with the PIKfyve complex. Whether APP family proteins can additionally form direct protein–protein interaction with PIKfyve or Fig4 remains to be explored. We show that APP binding to the PIKfyve complex drives formation of PI(3,5)P2 positive vesicles and that APP gene family members are required for supporting PIKfyve function. Interestingly, the PIKfyve complex is required for APP trafficking, suggesting a feedback loop in which APP, by binding to and stimulating PI(3,5)P2 vesicle formation may control its own trafficking. These data suggest that altered APP processing, as observed in Alzheimer’s disease, may disrupt PI(3,5)P2 metabolism, endosomal sorting and homeostasis with important implications for our understanding of the mechanism of neurodegeneration in Alzheimer’s disease

The amyloid precursor protein controls PIKfyve function

While the Amyloid Precursor Protein (APP) plays a central role in Alzheimer's disease, its cellular function still remains largely unclear. It was our goal to establish APP function which will provide insights into APP's implication in Alzheimer's disease. Using our recently developed proteo-liposome assay we established the interactome of APP's intracellular domain (known as AICD), thereby identifying novel APP interactors that provide mechanistic insights into APP function. By combining biochemical, cell biological and genetic approaches we validated the functional significance of one of these novel interactors. Here we show that APP binds the PIKfyve complex, an essential kinase for the synthesis of the endosomal phosphoinositide phosphatidylinositol-3,5-bisphosphate. This signalling lipid plays a crucial role in endosomal homeostasis and receptor sorting. Loss of PIKfyve function by mutation causes profound neurodegeneration in mammals. Using C. elegans genetics we demonstrate that APP functionally cooperates with PIKfyve in vivo. This regulation is required for maintaining endosomal and neuronal function. Our findings establish an unexpected role for APP in the regulation of endosomal phosphoinositide metabolism with dramatic consequences for endosomal biology and important implications for our understanding of Alzheimer's disease

Use of Disease-Modifying Therapies in Pediatric Relapsing-Remitting Multiple Sclerosis in the United Kingdom.

OBJECTIVES: To compare the real-world effectiveness of newer disease-modifying therapies (DMTs) vs injectables in children with relapsing-remitting multiple sclerosis (RRMS). METHODS: In this retrospective, multicenter study, from the UK Childhood Inflammatory Demyelination Network, we identified children with RRMS receiving DMTs from January 2012 to December 2018. Clinical and paraclinical data were retrieved from the medical records. Annualized relapse rates (ARRs) before and on treatment, time to relapse, time to new MRI lesions, and change in Expanded Disability Status Scale (EDSS) score were calculated. RESULTS: Of 103 children treated with DMTs, followed up for 3.8 years, relapses on treatment were recorded in 53/89 (59.5%) on injectables vs 8/54 (15%) on newer DMTs. The ARR was reduced from 1.9 to 1.1 on injectables (p < 0.001) vs 1.6 to 0.3 on newer DMTs (p = 0.002). New MRI lesions occurred in 77/89 (86.5%) of patients on injectables vs 26/54 (47%) on newer DMTs (p = 0.0001). Children on newer DMTs showed longer time to relapse, time to switch treatment, and time to new radiologic activity than patients on injectables (log-rank p < 0.01). After adjustment for potential confounders, multivariable analysis showed that injectables were associated with 12-fold increased risk of clinical relapse (adjusted hazard ratio [HR] = 12.12, 95% CI = 1.64-89.87, p = 0.015) and a 2-fold increased risk of new radiologic activity (adjusted HR = 2.78, 95% CI = 1.08-7.13, p = 0.034) compared with newer DMTs. At 2 years from treatment initiation, 38/103 (37%) patients had MRI activity in the absence of clinical relapses. The EDSS score did not change during the follow-up, and only 2 patients had cognitive impairment. CONCLUSION: Newer DMTs were associated with a lower risk of clinical and radiologic relapses in patients compared with injectables. Our study adds weight to the argument for an imminent shift in practice toward the use of newer, more efficacious DMTs in the first instance. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that newer DMTs (oral or infusions) are superior to injectables (interferon beta/glatiramer acetate) in reducing both clinical relapses and radiologic activity in children with RRMS

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum