Multi-omic approach characterises the neuroprotective role of retromer in regulating lysosomal health.

Retromer controls cellular homeostasis through regulating integral membrane protein sorting and transport and by controlling maturation of the endo-lysosomal network. Retromer dysfunction, which is linked to neurodegenerative disorders including Parkinson's and Alzheimer's diseases, manifests in complex cellular phenotypes, though the precise nature of this dysfunction, and its relation to neurodegeneration, remain unclear. Here, we perform an integrated multi-omics approach to provide precise insight into the impact of Retromer dysfunction on endo-lysosomal health and homeostasis within a human neuroglioma cell model. We quantify widespread changes to the lysosomal proteome, indicative of broad lysosomal dysfunction and inefficient autophagic lysosome reformation, coupled with a reconfigured cell surface proteome and secretome reflective of increased lysosomal exocytosis. Through this global proteomic approach and parallel transcriptomic analysis, we provide a holistic view of Retromer function in regulating lysosomal homeostasis and emphasise its role in neuroprotection.

Lack of Myosin X Enhances Osteoclastogenesis and Increases Cell Surface Unc5b in Osteoclast-Lineage Cells.

Normal bone mass is maintained by balanced bone formation and resorption. Myosin X (Myo10), an unconventional "myosin tail homology 4-band 4.1, ezrin, radixin, moesin" (MyTH4-FERM) domain containing myosin, is implicated in regulating osteoclast (OC) adhesion, podosome positioning, and differentiation in vitro. However, evidence is lacking for Myo10 in vivo function. Here we show that mice with Myo10 loss of function, Myo10m/m , exhibit osteoporotic deficits, which are likely due to the increased OC genesis and bone resorption because bone formation is unchanged. Similar deficits are detected in OC-selective Myo10 conditional knockout (cko) mice, indicating a cell autonomous function of Myo10. Further mechanistic studies suggest that Unc-5 Netrin receptor B (Unc5b) protein levels, in particular its cell surface level, are higher in the mutant OCs, but lower in RAW264.7 cells or HEK293 cells expressing Myo10. Suppressing Unc5b expression in bone marrow macrophages (BMMs) from Myo10m/m mice by infection with lentivirus of Unc5b shRNA markedly impaired RANKL-induced OC genesis. Netrin-1, a ligand of Unc5b, increased RANKL-induced OC formation in BMMs from both wild-type and Myo10m/m mice. Taken together, these results suggest that Myo10 plays a negative role in OC formation, likely by inhibiting Unc5b cell-surface targeting, and suppressing Netrin-1 promoted OC genesis. © 2019 American Society for Bone and Mineral Research.

Iron Chelation Inhibits Osteoclastic Differentiation In Vitro and in Tg2576 Mouse Model of Alzheimer's Disease.

Patients of Alzheimer's disease (AD) frequently have lower bone mineral density and higher rate of hip fracture. Tg2576, a well characterized AD animal model that ubiquitously express Swedish mutant amyloid precursor protein (APPswe), displays not only AD-relevant neuropathology, but also age-dependent bone deficits. However, the underlying mechanisms remain poorly understood. As APP is implicated as a regulator of iron export, and the metal chelation is considered as a potential therapeutic strategy for AD, we examined iron chelation's effect on the osteoporotic deficit in Tg2576 mice. Remarkably, in vivo treatment with iron chelator, clinoquinol (CQ), increased both trabecular and cortical bone-mass, selectively in Tg2576, but not wild type (WT) mice. Further in vitro studies showed that low concentrations of CQ as well as deferoxamine (DFO), another iron chelator, selectively inhibited osteoclast (OC) differentiation, without an obvious effect on osteoblast (OB) differentiation. Intriguingly, both CQ and DFO's inhibitory effect on OC was more potent in bone marrow macrophages (BMMs) from Tg2576 mice than that of wild type controls. The reduction of intracellular iron levels in BMMs by CQ was also more dramatic in APPswe-expressing BMMs. Taken together, these results demonstrate a potent inhibition on OC formation and activation in APPswe-expressing BMMs by iron chelation, and reveal a potential therapeutic value of CQ in treating AD-associated osteoporotic deficits.

NELF is a nuclear protein involved in hypothalamic GnRH neuronal migration.

Nasal embryonic LHRH factor (NELF) has been hypothesized to participate in the migration of GnRH and olfactory neurons into the forebrain, a prerequisite for normal hypothalamic-pituitary-gonadal function in puberty and reproduction. However, the biological functions of NELF, which has no homology to any human protein, remain largely elusive. Although mRNA expression did not differ, NELF protein expression was greater in migratory than postmigratory GnRH neurons. Pituitary Nelf mRNA expression was also observed and increased 3-fold after exogenous GnRH administration. Contrary to a previous report, NELF displayed predominant nuclear localization in GnRH neurons, confirmed by mutagenesis of a putative nuclear localization signal resulting in impaired nuclear expression. NELF knockdown impaired GnRH neuronal migration of NLT cells in vitro. These findings and the identification of two putative zinc fingers suggest that NELF could be a transcription factor. Collectively, our findings implicate NELF as a nuclear protein involved in the developmental function of the reproductive axis.