Microvesicle release from inner segments of healthy photoreceptors is a conserved phenomenon in mammalian species.

Many inherited visual diseases arise from mutations that affect the structure and function of photoreceptor cells. In some cases, the pathology is accompanied by a massive release of extracellular vesicles from affected photoreceptors. In this study, we addressed whether vesicular release is an exclusive response to ongoing pathology or a normal homeostatic phenomenon amplified in disease. We analyzed the ultrastructure of normal photoreceptors from both rod- and cone-dominant mammalian species and found that these cells release microvesicles budding from their inner segment compartment. Inner segment-derived microvesicles vary in their content, with some of them containing the visual pigment rhodopsin and others appearing to be interconnected with mitochondria. These data suggest the existence of a fundamental process whereby healthy mammalian photoreceptors release mistrafficked or damaged inner segment material as microvesicles into the interphotoreceptor space. This release may be greatly enhanced under pathological conditions associated with defects in protein targeting and trafficking. This article has an associated First Person interview with the first author of the paper.

Disruption of STIM1-mediated Ca2+ sensing and energy metabolism in adult skeletal muscle compromises exercise tolerance, proteostasis, and lean mass.

OBJECTIVE: Stromal interaction molecule 1 (STIM1) is a single-pass transmembrane endoplasmic/sarcoplasmic reticulum (E/SR) protein recognized for its role in a store operated Ca2+ entry (SOCE), an ancient and ubiquitous signaling pathway. Whereas STIM1 is known to be indispensable during development, its biological and metabolic functions in mature muscles remain unclear. METHODS: Conditional and tamoxifen inducible muscle STIM1 knock-out mouse models were coupled with multi-omics tools and comprehensive physiology to understand the role of STIM1 in regulating SOCE, mitochondrial quality and bioenergetics, and whole-body energy homeostasis. RESULTS: This study shows that STIM1 is abundant in adult skeletal muscle, upregulated by exercise, and is present at SR-mitochondria interfaces. Inducible tissue-specific deletion of STIM1 (iSTIM1 KO) in adult muscle led to diminished lean mass, reduced exercise capacity, and perturbed fuel selection in the settings of energetic stress, without affecting whole-body glucose tolerance. Proteomics and phospho-proteomics analyses of iSTIM1 KO muscles revealed molecular signatures of low-grade E/SR stress and broad activation of processes and signaling networks involved in proteostasis. CONCLUSION: These results show that STIM1 regulates cellular and mitochondrial Ca2+ dynamics, energy metabolism and proteostasis in adult skeletal muscles. Furthermore, these findings provide insight into the pathophysiology of muscle diseases linked to disturbances in STIM1-dependent Ca2+ handling.

Pillararenes: fascinating planar chiral macrocyclic arenes.

Chiral macrocycles possess significant value in chiral science and supramolecular chemistry. Pillararenes, as a class of relatively young supramolecular macrocyclic hosts, have been widely used for host-guest recognition and self-assembly. Since the position of substituents on the benzene rings breaks the molecular symmetry (symmetric plane and symmetric center), pillararenes possess planar chirality. However, it is a great challenge to synthesize stable and resolvable enantiomers because of the easy rotation of the phenylene group. In this review, we summarize the construction methods of resolvable chiral pillararenes. We also focus on their applications in enantioselective recognition, chiral switches, chirality sensing, asymmetric catalysis, circularly polarized luminescence, metal-organic frameworks, and highly permeable membranes. Finally, we discuss the future research perspectives in this field of pillararene-based planar chiral materials. We hope that this review will encourage more researchers to work in this exciting field.

Morphology transformation of pillararene-based supramolecular nanostructures.

Supramolecular nanostructures (SNSs) have received significant attention in recent years since they endow specific and unique properties to materials. Pillararenes, as a novel group of macrocyclic molecules, present particular features such as ease of modification, more electron-rich cavity as well as captivating host-guest chemistry, thus bestowing them with the abilities to fabricate intriguing SNSs. This feature article highlights the construction methods of pillararene-based supramolecular nanostructures (PSNSs), where most of which are in aqueous media, and the factors that influence the morphological transformation of PSNSs. Moreover, the structure-function relationship of divergent PSNSs is clarified. Finally, the future challenges and perspectives for PSNSs are pointed out and discussed. We hope this review will benefit the researchers interested in engineering PSNSs with on demand morphologies and desired functions.

An azine-containing bispillar[5]arene-based multi-stimuli responsive supramolecular pseudopolyrotaxane gel for effective adsorption of rhodamine B.

An azine-containing bispillar[5]arene was designed and synthesized by the reaction of aldehyde functionalized-pillar[5]arene and hydrazine. Then, a novel bispillar[5]arene-based supramolecular pseudopolyrotaxane has been successfully prepared via host-guest interaction. Interestingly, by taking advantage of the host-guest interactions, π-π stacking interactions and hydrogen bonding interactions, the multi-stimuli-responsive gel-sol phase transitions of such a supramolecular pseudopolyrotaxane gel were successfully realized under different stimuli, such as acid, temperature, concentration, and competitive guests. Moreover, this supramolecular system could effectively adsorb dye molecule rhodamine B. It is worth noting that this supramolecular pseudopolyrotaxane gel prepared in cyclohexanol solution (BP5·G·C) could be used as an adsorbent material for adsorbing rhodamine B with adsorption efficiency of 98.4%. Meanwhile, the adsorption efficiency was 97.6% for supramolecular pseudopolyrotaxane gel prepared in DMSO-H2O (v : v, 8 : 2) binary solution (BP5·G·D), also indicating the superior adsorption effect of BP5·G·D toward the dye molecule rhodamine B.

PRCD is essential for high-fidelity photoreceptor disc formation.

Progressive rod-cone degeneration (PRCD) is a small protein residing in the light-sensitive disc membranes of the photoreceptor outer segment. Until now, the function of PRCD has remained enigmatic despite multiple demonstrations that its mutations cause blindness in humans and dogs. Here, we generated a PRCD knockout mouse and observed a striking defect in disc morphogenesis, whereby newly forming discs do not properly flatten. This leads to the budding of disc-derived vesicles, specifically at the site of disc morphogenesis, which accumulate in the interphotoreceptor matrix. The defect in nascent disc flattening only minimally alters the photoreceptor outer segment architecture beyond the site of new disc formation and does not affect the abundance of outer segment proteins and the photoreceptor's ability to generate responses to light. Interestingly, the retinal pigment epithelium, responsible for normal phagocytosis of shed outer segment material, lacks the capacity to clear the disc-derived vesicles. This deficiency is partially compensated by a unique pattern of microglial migration to the site of disc formation where they actively phagocytize vesicles. However, the microglial response is insufficient to prevent vesicular accumulation and photoreceptors of PRCD knockout mice undergo slow, progressive degeneration. Taken together, these data show that the function of PRCD is to keep evaginating membranes of new discs tightly apposed to each other, which is essential for the high fidelity of photoreceptor disc morphogenesis and photoreceptor survival.

Human complement factor H Y402H polymorphism causes an age-related macular degeneration phenotype and lipoprotein dysregulation in mice.

One of the strongest susceptibility genes for age-related macular degeneration (AMD) is complement factor H (CFH); however, its impact on AMD pathobiology remains unresolved. Here, the effect of the principal AMD-risk-associated CFH variant (Y402H) on the development and progression of age-dependent AMD-like pathologies was determined in vivo. Transgenic mice expressing equal amounts of the full-length normal human CFH Y402 (CFH-Y/0) or the AMD-risk associated CFH H402 (CFH-H/H) variant on a Cfh-/- background were aged to 90 weeks and switched from normal diet (ND) to a high fat, cholesterol-enriched (HFC) diet for 8 weeks. The resulting phenotype was compared with age-matched controls maintained on ND. Remarkably, an AMD-like phenotype consisting of vision loss, increased retinal pigmented epithelium (RPE) stress, and increased basal laminar deposits was detected only in aged CFH-H/H mice following the HFC diet. These changes were not observed in aged CFH-Y/0 mice or in younger (36- to 40-week-old) CFH mice of both genotypes fed either diet. Biochemical analyses of aged CFH mice after HFC diet revealed genotype-dependent changes in plasma and eyecup lipoproteins, but not complement activation, which correlated with the AMD-like phenotype in old CFH-H/H mice. Specifically, apolipoproteins B48 and A1 are elevated in the RPE/choroid of the aged CFH-H/H mice compared with age-matched control CFH-Y/0 fed a HFC diet. Hence, we demonstrate a functional consequence of the Y402H polymorphism in vivo, which promotes AMD-like pathology development and affects lipoprotein levels in aged mice. These findings support targeting lipoproteins as a viable therapeutic strategy for treating AMD.

Deficiency of Shank2 causes mania-like behavior that responds to mood stabilizers.

Genetic defects in the synaptic scaffolding protein gene, SHANK2, are linked to a variety of neuropsychiatric disorders, including autism spectrum disorders, schizophrenia, intellectual disability, and bipolar disorder, but the molecular mechanisms underlying the pleotropic effects of SHANK2 mutations are poorly understood. We generated and characterized a line of Shank2 mutant mice by deleting exon 24 (Δe24). Shank2Δe24-/- mice engage in significantly increased locomotor activity, display abnormal reward-seeking behavior, are anhedonic, have perturbations in circadian rhythms, and show deficits in social and cognitive behaviors. While these phenotypes recapitulate the pleotropic behaviors associated with human SHANK2-related disorders, major behavioral features in these mice are reminiscent of bipolar disorder. For instance, their hyperactivity was augmented with amphetamine but was normalized with the mood stabilizers lithium and valproate. Shank2 deficiency limited to the forebrain recapitulated the bipolar mania phenotype. The composition and functions of NMDA and AMPA receptors were altered at Shank2-deficient synapses, hinting toward the mechanism underlying these behavioral abnormalities. Human genetic findings support construct validity, and the behavioral features in Shank2 Δe24 mice support face and predictive validities of this model for bipolar mania. Further genetic studies to understand the contribution of SHANK2 deficiencies in bipolar disorder are warranted.

A pillar[5]arene-based multiple-stimuli responsive metal-organic gel was constructed for facile removal of mercury ions.

A thioacetohydrazide functionalized pillar[5]arene was synthesized, which could further assemble into a linear supramolecular metal-organic polymer upon adding Zn2+. Furthermore, the obtained linear supramolecular metal-organic polymer could self-assemble to form a fluorescent supramolecular metal-organic gel at high concentration. When TBAOH was added to the viscous solution at high temperature, the obtained solution could not form a supramolecular metal-organic gel upon cooling. More importantly, when Hg2+ ions are added to the metal-organic gel, the strong blue fluorescence is clearly quenched, and this metal-organic gel (xerogel) could effectively remove Hg2+ from water. Simultaneously, a thin film based on the metal-organic gel was prepared, which was confirmed to be a convenient test kit for detecting Hg2+.

Photoreceptor discs form through peripherin-dependent suppression of ciliary ectosome release.

The primary cilium is a highly conserved organelle housing specialized molecules responsible for receiving and processing extracellular signals. A recently discovered property shared across many cilia is the ability to release small vesicles called ectosomes, which are used for exchanging protein and genetic material among cells. In this study, we report a novel role for ciliary ectosomes in building the elaborate photoreceptor outer segment filled with hundreds of tightly packed "disc" membranes. We demonstrate that the photoreceptor cilium has an innate ability to release massive amounts of ectosomes. However, this process is suppressed by the disc-specific protein peripherin, which enables retained ectosomes to be morphed into discs. This new function of peripherin is performed independently from its well-established role in maintaining the high curvature of disc edges, and each function is fulfilled by a separate part of peripherin's molecule. Our findings explain how the outer segment structure evolved from the primary cilium to provide photoreceptor cells with vast membrane surfaces for efficient light capture.

PPARß/δ selectively regulates phenotypic features of age-related macular degeneration.

Peroxisome proliferator-activated receptor-ß/δ (PPARß/δ) is a nuclear receptor that regulates differentiation, inflammation, lipid metabolism, extracellular matrix remodeling, and angiogenesis in multiple tissues. These pathways are also central to the pathogenesis of age-related macular degeneration (AMD), the leading cause of vision loss globally. With the goal of identifying signaling pathways that may be important in the development of AMD, we investigated the impact of PPARß/δ activation on ocular tissues affected in the disease. PPARß/δ is expressed and can be activated in AMD vulnerable cells, including retinal pigment epithelial (RPE) and choroidal endothelial cells. Further, PPARß/δ knockdown modulates AMD-related pathways selectively. Specifically, genetic ablation of Pparß/δ in aged mice resulted in exacerbation of several phenotypic features of early dry AMD, but attenuation of experimentally induced choroidal neovascular (CNV) lesions. Antagonizing PPARß/δ in both in vitro angiogenesis assays and in the in vivo experimentally induced CNV model, inhibited angiogenesis and angiogenic pathways, while ligand activation of PPARß/δ, in vitro, decreased RPE lipid accumulation, characteristic of dry AMD. This study demonstrates for the first time, selective regulation of a nuclear receptor in the eye and establishes that selective targeting of PPARß/δ may be a suitable strategy for treatment of different clinical sub-types of AMD.

Altered mGluR5-Homer scaffolds and corticostriatal connectivity in a Shank3 complete knockout model of autism.

Human neuroimaging studies suggest that aberrant neural connectivity underlies behavioural deficits in autism spectrum disorders (ASDs), but the molecular and neural circuit mechanisms underlying ASDs remain elusive. Here, we describe a complete knockout mouse model of the autism-associated Shank3 gene, with a deletion of exons 4-22 (Δe4-22). Both mGluR5-Homer scaffolds and mGluR5-mediated signalling are selectively altered in striatal neurons. These changes are associated with perturbed function at striatal synapses, abnormal brain morphology, aberrant structural connectivity and ASD-like behaviour. In vivo recording reveals that the cortico-striatal-thalamic circuit is tonically hyperactive in mutants, but becomes hypoactive during social behaviour. Manipulation of mGluR5 activity attenuates excessive grooming and instrumental learning differentially, and rescues impaired striatal synaptic plasticity in Δe4-22(-/-) mice. These findings show that deficiency of Shank3 can impair mGluR5-Homer scaffolding, resulting in cortico-striatal circuit abnormalities that underlie deficits in learning and ASD-like behaviours. These data suggest causal links between genetic, molecular, and circuit mechanisms underlying the pathophysiology of ASDs.

Discs of mammalian rod photoreceptors form through the membrane evagination mechanism.

Photoreceptor discs are membrane organelles harboring components of the visual signal transduction pathway. The mechanism by which discs form remains enigmatic and is the subject of a major controversy. Classical studies suggest that discs are formed as serial plasma membrane evaginations, whereas a recent alternative postulates that discs, at least in mammalian rods, are formed through intracellular vesicular fusion. We evaluated these models in mouse rods using methods that distinguish between the intracellular vesicular structures and plasma membrane folds independently of their appearance in electron micrographs. The first differentiated membranes exposed to the extracellular space from intracellular membranes; the second interrogated the orientation of protein molecules in new discs. Both approaches revealed that new discs are plasma membrane evaginations. We further demonstrated that vesiculation and plasma membrane enclosure at the site of new disc formation are artifacts of tissue fixation. These data indicate that all vertebrate photoreceptors use the evolutionary conserved membrane evagination mechanism to build their discs.

Expression of human complement factor H prevents age-related macular degeneration-like retina damage and kidney abnormalities in aged Cfh knockout mice.

Complement factor H (CFH) is an important regulatory protein in the alternative pathway of the complement system, and CFH polymorphisms increase the genetic risk of age-related macular degeneration dramatically. These same human CFH variants have also been associated with dense deposit disease. To mechanistically study the function of CFH in the pathogenesis of these diseases, we created transgenic mouse lines using human CFH bacterial artificial chromosomes expressing full-length human CFH variants and crossed these to Cfh knockout (Cfh(-/-)) mice. Human CFH protein inhibited cleavage of mouse complement component 3 and factor B in plasma and in retinal pigment epithelium/choroid/sclera, establishing that human CFH regulates activation of the mouse alternative pathway. One of the mouse lines, which express relatively higher levels of CFH, demonstrated functional and structural protection of the retina owing to the Cfh deletion. Impaired visual function, detected as a deficit in the scotopic electroretinographic response, was improved in this transgenic mouse line compared with Cfh(-/-) mice, and transgenics had a thicker outer nuclear layer and less sub-retinal pigment epithelium deposit accumulation. In addition, expression of human CFH also completely protected the mice from developing kidney abnormalities associated with loss of CFH. These humanized CFH mice present a valuable model for study of the molecular mechanisms of age-related macular degeneration and dense deposit disease and for testing therapeutic targets.

The role of complement dysregulation in AMD mouse models.

Variations in several complement genes are now known to be significant risk factors for the development of age-related macular degeneration (AMD). Despite dramatic effects on disease susceptibility, the underlying mechanisms by which common polymorphisms in complement proteins alter disease risk have remained unclear. Genetically modified mice in which the activity of the complement has been altered are available and can be used to investigate the role of complement in the pathogenesis of AMD. In this mini review, we will discuss some existing complement models of AMD and our efforts to develop and characterize the ocular phenotype in a variety of mice in which complement is either chronically activated or inhibited. A spectrum of complement dysregulation was modeled on the APOE4 AMD mouse model by crossing these mice to complement factor H knockout (cfh-/-) mice to test the impact of excess complement activation, and by crossing them to soluble-complement-receptor-1-related protein y (sCrry) mice, in which sCrry acts as a potent inhibitor of mouse complement acting in a manner similar to CFH. In addition, we have also generated humanized CFH mice expressing normal and risk variants of CFH.

Subcellular organization of camkii in rat hippocampal pyramidal neurons.

Calcium/calmodulin-dependent protein kinase II (CaMKII) plays a key role in N-methyl-D-aspartate (NMDA) receptor-dependent long-term synaptic plasticity; its location is critical for signal transduction, and may provide clues that further elucidate its function. We therefore examined the subcellular localization of CaMKII in CA1 stratum radiatum of adult rat hippocampus, by using immuno-electron microscopy after chemical fixation. When tissue was fixed quickly, the concentration of CaMKIIα (assessed by pre-embedding immunogold) was significantly higher in dendritic shafts than in spine heads. However, when tissue was fixed 5 minutes after perfusion with normal saline, the density of labeling decreased in dendritic shaft while increasing in spine heads, implying rapid translocation into the spine during brief perimortem stress. Likewise, in quickly fixed tissue, CaMKII within spine heads was found at comparable concentrations in the "proximal" half (adjacent to the spine neck) and the "distal" half (containing the postsynaptic density [PSD]), whereas after delayed fixation, label density increased in the distal side of the spine head, suggesting that CaMKII within the spine head moves toward the PSD during this interval. To estimate its distribution at the synapse in vivo, we performed postembedding immunogold staining for CaMKII in quick-fixed tissue, and found that the enzyme did not concentrate primarily within the central matrix of the PSD. Instead, labeling density peaked ∼40 nm inside the postsynaptic membrane, at the cytoplasmic fringe of the PSD. Labeling within 25 nm of the postsynaptic membrane concentrated at the lateral edge of the synapse. This lateral "PSD core" pool of CaMKII may play a special role in synaptic plasticity.

STIM1-Ca(2+) signaling is required for the hypertrophic growth of skeletal muscle in mice.

Immediately after birth, skeletal muscle must undergo an enormous period of growth and differentiation that is coordinated by several intertwined growth signaling pathways. How these pathways are integrated remains unclear but is likely to involve skeletal muscle contractile activity and calcium (Ca(2+)) signaling. Here, we show that Ca(2+) signaling governed by stromal interaction molecule 1 (STIM1) plays a central role in the integration of signaling and, therefore, muscle growth and differentiation. Conditional deletion of STIM1 from the skeletal muscle of mice (mSTIM1(-/-) mice) leads to profound growth delay, reduced myonuclear proliferation, and perinatal lethality. We show that muscle fibers of neonatal mSTIM1(-/-) mice cannot support the activity-dependent Ca(2+) transients evoked by tonic neurostimulation, even though excitation contraction coupling (ECC) remains unperturbed. In addition, disruption of tonic Ca(2+) signaling in muscle fibers attenuates downstream muscle growth signaling, such as that of calcineurin, mitogen-activated protein (MAP) kinases, extracellular signal-regulated kinase 1 and 2 (ERK1/2), and AKT. Based on our findings, we propose a model wherein STIM1-mediated store-operated calcium entry (SOCE) governs the Ca(2+) signaling required for cellular processes that are necessary for neonatal muscle growth and differentiation.

Anti-amyloid therapy protects against retinal pigmented epithelium damage and vision loss in a model of age-related macular degeneration.

Age-related macular degeneration (AMD) is a leading cause of visual dysfunction worldwide. Amyloid ß (Aß) peptides, Aß1-40 (Aß40) and Aß1-42 (Aß42), have been implicated previously in the AMD disease process. Consistent with a pathogenic role for Aß, we show here that a mouse model of AMD that invokes multiple factors that are known to modify AMD risk (aged human apolipoprotein E 4 targeted replacement mice on a high-fat, cholesterol-enriched diet) presents with Aß-containing deposits basal to the retinal pigmented epithelium (RPE), histopathologic changes in the RPE, and a deficit in scotopic electroretinographic response, which is reflective of impaired visual function. Strikingly, these electroretinographic deficits are abrogated in a dose-dependent manner by systemic administration of an antibody targeting the C termini of Aß40 and Aß42. Concomitant reduction in the levels of Aß and activated complement components in sub-RPE deposits and structural preservation of the RPE are associated with anti-Aß40/42 antibody immunotherapy and visual protection. These observations are consistent with the reduction in amyloid plaques and improvement of cognitive function in mouse models of Alzheimer's disease treated with anti-Aß antibodies. They also implicate Aß in the pathogenesis of AMD and identify Aß as a viable therapeutic target for its treatment.

Heparan sulfate, including that in Bruch's membrane, inhibits the complement alternative pathway: implications for age-related macular degeneration.

An imbalance between activation and inhibition of the complement system has been implicated in the etiologies of numerous common diseases. Allotypic variants of a key complement fluid-phase regulatory protein, complement factor H (CFH), are strongly associated with age-related macular degeneration (AMD), a leading cause of worldwide visual dysfunction, although its specific role in AMD pathogenesis is still not clear. CFH was isolated from individuals carrying combinations of two of the nonsynonymous coding variants most strongly associated with AMD risk, V62/H402 (risk haplotype variants), I62/Y402 (nonrisk haplotype variants), and V62/Y402. These proteins were used in two functional assays (cell surface- and fluid-phase-based) measuring cofactor activity of CFH in the factor I-mediated cleavage of C3b. Although no variant-specific differences in the cofactor activity were detected, when heparan sulfate (HS) was added to these assays, it accelerated the rate of C3b cleavage, and this effect could be modulated by degree of HS sulfation. Bruch's membrane/choroid, a site of tissue damage in AMD, contains high concentrations of glycosaminoglycans, including HS. Addition of human Bruch's membrane/choroid to the fluid-phase assay accelerated the C3b cleavage, and this effect was lost posttreatment of the tissue with heparinase III. Binding of CFH variants to Bruch's membrane/choroid isolated from elderly, non-AMD donor eyes, was similar, as was the functional activity of bound CFH. These findings refine our understanding of interactions of HS and complement and support the hypothesis that these interactions play a role in the transition between normal aging and AMD in Bruch's membrane/choroid.

Targeting age-related macular degeneration with Alzheimer's disease based immunotherapies: anti-amyloid-beta antibody attenuates pathologies in an age-related macular degeneration mouse model.

Age-related macular degeneration (AMD) is a late-onset, neurodegenerative retinal disease that shares several clinical and pathological features with Alzheimer's disease (AD) including extracellular deposits containing amyloid-beta (Abeta) peptides. Immunotherapy targeting the Abeta protein has been investigated as a potential treatment for AD. Here, we present the rationale for extending this approach to treat AMD. We tested an anti-Abeta antibody administered systemically in a mouse model of AMD. Histological and functional measurements in treated animals compared to controls showed that following immunotherapy, the amounts of Abeta in the retina and brain were decreased and the ERG deficits in the retina were attenuated. These data support the hypothesis that Abeta is a therapeutic target for AMD.