Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.Non-small cell lung cancer (NSCLC) is often characterized by mutually exclusive mutations in the epidermal growth factor receptor (EGFR) or the guanosine triphosphatase KRAS. We hypothesized that blocking EGFR palmitoylation, previously shown to inhibit EGFR activity, might alter downstream signaling in the KRAS-mutant setting. Here, we found that blocking EGFR palmitoylation, by either knocking down the palmitoyltransferase DHHC20 or expressing a palmitoylation-resistant EGFR mutant, reduced activation of the kinase PI3K, the abundance of the transcription factor MYC, and the proliferation of cells in culture, as well as reduced tumor growth in a mouse model of KRAS-mutant lung adenocarcinoma. Knocking down DHHC20 reduced the growth of existing tumors derived from human KRAS-mutant lung cancer cells and increased the sensitivity of these cells to a PI3K inhibitor. Palmitoylated EGFR interacted with the PI3K regulatory subunit PIK3R1 (p85) and increased the recruitment of the PI3K heterodimer to the plasma membrane. Alternatively, blocking palmitoylation increased the association of EGFR with the MAPK adaptor Grb2 and decreased that with p85. This binary switching between MAPK and PI3K signaling, modulated by EGFR palmitoylation, was only observed in the presence of oncogenic KRAS. These findings suggest a mechanism whereby oncogenic KRAS saturates signaling through unpalmitoylated EGFR, reducing formation of the PI3K signaling complex. Future development of DHHC20 inhibitors to reduce EGFR-PI3K signaling could be beneficial to patients with KRAS-mutant tumors. Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.Krabbe's disease is an infantile neurodegenerative disease, affected by mutations in the lysosomal enzyme galactocerebrosidase, leading to the accumulation of its metabolite psychosine. We have shown previously that the S1P receptor agonist fingolimod (FTY720) attenuates psychosine-induced glial cell death and demyelination both in vitro and ex vivo models. This data, together with a lack of therapies for Krabbe's disease, prompted the current preclinical study examining the effects of fingolimod in twitcher mice, a murine model of Krabbe's disease. Twitcher mice, both male and female, carrying a natural mutation in the GALC gene were given fingolimod via drinking water (1mg/kg/day). The direct impact of fingolimod administration was assessed via histochemical and biochemical analysis using markers of myelin, astrocytes, microglia, neurons, globoid and immune cells. The effects of fingolimod on twitching behaviour and lifespan was also demonstrated. Our results show that treatment of twitcher mice with fingolimod significantly rescued myelin levels compared to vehicle treated animals and also regulated astrocyte and microglial reactivity. Furthermore, non-phosphorylated neurofilament levels were decreased indicating neuroprotective and neurorestorative processes. These protective effects of fingolimod on twitcher mice brain pathology, was reflected by an increased lifespan of fingolimod treated twitcher mice. These in vivo findings corroborate initial in vitro studies and highlight the potential use of S1P receptors as drug targets for Krabbe's disease.Significance StatementThis study demonstrates that administration of the therapy, known as fingolimod, in a mouse model of Krabbe's disease (namely, the twitcher mouse model) significantly rescues myelin levels. Further, this drug fingolimod, also regulates the reactivity of glial cells, astrocyte and microglia, in this mouse model. These protective effects of fingolimod result in an increased lifespan of twitcher mice. Copyright © 2020 Béchet et al.The extraordinary diversity of excitatory synapse sizes is commonly attributed to activity-dependent processes that drive synaptic growth and diminution. Recent studies also point to activity-independent size fluctuations, possibly driven by innate synaptic molecule dynamics, as important generators of size diversity. To examine the contributions of activity-dependent and independent processes to excitatory synapse size diversity, we studied glutamatergic synapse size dynamics and diversification in cultured rat cortical neurons (both sexes), silenced from plating. We found that in networks with no history of activity whatsoever, synaptic size diversity was no less extensive than that observed in spontaneously active networks. Synapses in silenced networks were larger, size distributions were broader, yet these were rightward-skewed and similar in shape when scaled by mean synaptic size. Silencing reduced the magnitude of size fluctuations and weakened constraints on size distributions, yet these were sufficidiversity is commonly thought to reflect the outcome of activity-dependent forms of synaptic plasticity, yet activity-independent processes might also play some part. Here we show that in neurons with no history of activity whatsoever, synaptic sizes are no less diverse. We show that this diversity is the product of activity-independent size fluctuations, which are sufficient to generate a full repertoire of synaptic sizes at correct proportions. By combining modeling and experimentation we expose reciprocal relationships between size fluctuations, synaptic sizes and synaptic counts, and show how these phenomena might be connected through the dynamics of synaptic molecules as they move in, out and between synapses. Copyright © 2020 the authors.Navigation often requires movement in three-dimensional (3D) space. Recent studies have postulated two different models for how head direction (HD) cells encode 3D space - the rotational-plane hypothesis and the dual-axis model. To distinguish these models, we recorded HD cells in female rats while they traveled different routes along both horizontal and vertical surfaces from an elevated platform to the top of a cuboidal apparatus. We compared HD cell preferred firing directions (PFDs) in different planes and addressed the issue of whether HD cell firing is commutative - does the order of the animal's route affect the final outcome of the cell's PFD? Rats locomoted a direct or indirect route from the floor to the cube top via 1, 2, or 3 vertical walls. https://www.selleckchem.com/products/pclx-001-ddd86481.html While the rotational-plane hypothesis accounted for PFD shifts when the animal traversed horizontal corners, the cell's PFD was better explained by the dual-axis model when the animal traversed vertical corners. Responses also followed the dual-axis model 1) under dark conditions, 2) for passive movement of the rat, 3) following apparatus rotation, 4) for movement around inside vertical corners, and 5) across a 45° outside vertical corner.