KIF13B enhances the endocytosis of LRP1 by recruiting LRP1 to caveolae

Motor protein KIF13B orchestrates hepatic metabolism to prevent metabolic dysfunction-associated fatty liver disease

BACKGROUND

Kinesin family member 13B (KIF13B), a crucial motor protein, exerts multiple cellular biological functions. However, the implication of KIF13B in metabolic dysfunction-associated fatty liver disease (MAFLD) has not been explored yet. This study aimed to investigate KIF13B's role and underlying mechanism in MAFLD and proposes it as a potential pharmacological target.

METHODS

We assessed KIF13B expression in MAFLD patients and rodent models. The roles of Kif13b in lipid metabolism and MAFLD were investigated using whole-body Kif13b knockout mice, hepatocyte-specific Kif13b-deficient mice and hamsters exposed to different diets. The underlying mechanisms by which Kif13b governed hepatic lipid homeostasis and MAFLD progression were explored in vitro. Finally, the Kif13b's impact on atherosclerotic development was studied in the context of MAFLD.

RESULTS

KIF13B expression was reduced in patients and murine models with MAFLD. Rodents with global or liver-specific knockout of the Kif13b gene exhibit spontaneous hepatic steatosis, which is further exacerbated by different overnutrition diets. Overexpression of human KIF13B by lentivirus effectively prevented metabolic dysfunction-associated steatohepatitis (MASH) in methionine-choline-deficient diet (MCD)-fed mice. Furthermore, Kif13b deficiency accelerates atherosclerosis in the context of MAFLD. Mechanistically, Kif13b depletion increases hepatic lipid synthesis and impairs mitochondrial oxidative phosphorylation. Further screening reveals that Kif13b interacts with AMP-activated catalytic subunit alpha 1 (AMPKα1) to regulate the phosphorylation of AMPKα1, governing mitochondrial homeostasis and suppressing sterol regulatory element binding protein 1 (Srebp1)-mediated de novo lipogenesis in the liver.

CONCLUSION

This work establishes a causal relationship between KIF13B deficiency and MAFLD, emphasizing KIF13B as a potential therapeutic target for treating MAFLD.

Targeting Kinesins for Therapeutic Exploitation of Chromosomal Instability in Lung Cancer

New therapeutic approaches that antagonize tumour-promoting phenotypes in lung cancer are needed to improve patient outcomes. Chromosomal instability (CIN) is a hallmark of lung cancer characterized by the ongoing acquisition of genetic alterations that include the gain and loss of whole chromosomes or segments of chromosomes as well as chromosomal rearrangements during cell division. Although it provides genetic diversity that fuels tumour evolution and enables the acquisition of aggressive phenotypes like immune evasion, metastasis, and drug resistance, too much CIN can be lethal because it creates genetic imbalances that disrupt essential genes and induce severe proteotoxic and metabolic stress. As such, sustaining advantageous levels of CIN that are compatible with survival is a fine balance in cancer cells, and potentiating CIN to levels that exceed a tolerable threshold is a promising treatment strategy for inherently unstable tumours like lung cancer. Kinesins are a superfamily of motor proteins with many members having functions in mitosis that are critical for the correct segregation of chromosomes and, consequently, maintaining genomic integrity. Accordingly, inhibition of such kinesins has been shown to exacerbate CIN. Therefore, inhibiting mitotic kinesins represents a promising strategy for amplifying CIN to lethal levels in vulnerable cancer cells. In this review, we describe the concept of CIN as a therapeutic vulnerability and comprehensively summarize studies reporting the clinical and functional relevance of kinesins in lung cancer, with the goal of outlining how kinesin inhibition, or "targeting kinesins", holds great potential as an effective strategy for treating lung cancer.

Exosomal Bupivacaine: Integrating Nerve Barrier Penetration Capability and Sustained Drug Release for Enhanced Potency in Peripheral Nerve Block and Reduced Toxicity

Peripherally injected local anesthetics exhibit limited ability to penetrate peripheral nerve barriers (PNBs), which limits their effectiveness in peripheral nerve block and increases the risk of adverse effects. In this work, we demonstrated that exosomes derived from Human Embryo Kidney (HEK) 293 cells can effectively traverse the perineurium, which is the rate-limiting barrier within PNBs that local anesthetics need to cross before acting on axons. Based on this finding, we use these exosomes as a carrier for bupivacaine (BUP), a local anesthetic commonly used in clinical settings. The in vitro assessments revealed that the prepared exosomal bupivacaine (BUP@EXO) achieves a BUP loading capacity of up to 82.33% and sustained release of BUP for over 30 days. In rats, a single peripheral injection of BUP@EXO, containing 0.75 mg of BUP, which is ineffective for BUP alone, induced a 2-hour sensory nerve blockade without significant motor impairments. Increasing the BUP dose in BUP@EXO to 2.5 mg, a highly toxic dose for BUP alone, extended the sensory nerve blockade to 12 hours without causing systemic cardiotoxicity and local neurotoxicity and myotoxicity.

Time-resolved proximity proteomics uncovers a membrane tension-sensitive caveolin-1 interactome at the rear of migrating cells

Caveolae are small membrane pits with fundamental roles in mechanotransduction. Several studies have shown that caveolae flatten out in response to increased membrane tension, thereby acting as a mechanosensitive membrane reservoir that buffers acute mechanical stress. Caveolae have also been implicated in the control of RhoA/ROCK-mediated actomyosin contractility at the rear of migrating cells. However, how membrane tension controls the organisation of caveolae and their role in mechanotransduction remains unclear. To address this, we systematically quantified protein-protein interactions of caveolin-1 in migrating RPE1 cells at steady state and in response to an acute increase in membrane tension using biotin-based proximity labelling and quantitative mass spectrometry. Our data show that caveolae are highly enriched at the rear of migrating RPE1 cells and that membrane tension rapidly and reversibly disrupts the caveolar protein coat. Membrane tension also detaches caveolin-1 from focal adhesion proteins and several mechanosensitive regulators of cortical actin including filamins and cortactin. In addition, we present evidence that ROCK and the RhoGAP ARHGAP29 associate with caveolin-1 in a manner dependent on membrane tension, with ARHGAP29 influencing caveolin-1 Y14 phosphorylation, caveolae rear localisation, and RPE1 cell migration. Taken together, our work uncovers a membrane tension-sensitive coupling between caveolae and the rear-localised F-actin cytoskeleton. This provides a framework for dissecting the molecular mechanisms underlying caveolae-regulated mechanotransduction pathways.

DLG1 functions upstream of SDCCAG3 and IFT20 to control ciliary targeting of polycystin-2

Polarized vesicular trafficking directs specific receptors and ion channels to cilia, but the underlying mechanisms are poorly understood. Here we describe a role for DLG1, a core component of the Scribble polarity complex, in regulating ciliary protein trafficking in kidney epithelial cells. Conditional knockout of Dlg1 in mouse kidney causes ciliary elongation and cystogenesis, and cell-based proximity labeling proteomics and fluorescence microscopy show alterations in the ciliary proteome upon loss of DLG1. Specifically, the retromer-associated protein SDCCAG3, IFT20, and polycystin-2 (PC2) are reduced in the cilia of DLG1-deficient cells compared to control cells. This phenotype is recapitulated in vivo and rescuable by re-expression of wild-type DLG1, but not a Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)-associated DLG1 variant, p.T489R. Finally, biochemical approaches and Alpha Fold modelling suggest that SDCCAG3 and IFT20 form a complex that associates, at least indirectly, with DLG1. Our work identifies a key role for DLG1 in regulating ciliary protein composition and suggests that ciliary dysfunction of the p.T489R DLG1 variant may contribute to CAKUT.

DLG1 functions upstream of SDCCAG3 and IFT20 to control ciliary targeting of polycystin-2

Polarized vesicular trafficking directs specific receptors and ion channels to cilia, but the underlying mechanisms are poorly understood. Here we describe a role for DLG1, a core component of the Scribble polarity complex, in regulating ciliary protein trafficking in kidney epithelial cells. Conditional knockout of Dlg1 in mouse kidney caused ciliary elongation and cystogenesis, and cell-based proximity labelling proteomics and fluorescence microscopy showed alterations in the ciliary proteome upon loss of DLG1. Specifically, the retromer-associated protein SDCCAG3, IFT20 and polycystin-2 (PC2) were reduced in cilia of DLG1 deficient cells compared to control cells. This phenotype was recapitulated in vivo and rescuable by re-expression of wildtype DLG1, but not a Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)-associated DLG1 variant, p.T489R. Finally, biochemical approaches and Alpha Fold modelling suggested that SDCCAG3 and IFT20 form a complex that associates, at least indirectly, with DLG1. Our work identifies a key role for DLG1 in regulating ciliary protein composition and suggests that ciliary dysfunction of the p.T489R DLG1 variant may contribute to CAKUT.

IGFBP5 is released by senescent cells and is internalized by healthy cells, promoting their senescence through interaction with retinoic receptors

Cells that are exposed to harmful genetic damage, either from internal or external sources, may undergo senescence if they are unable to repair their DNA. Senescence, characterized by a state of irreversible growth arrest, can spread to neighboring cells through a process known as the senescence-associated secretory phenotype (SASP). This phenomenon contributes to both aging and the development of cancer. The SASP comprises a variety of factors that regulate numerous functions, including the induction of secondary senescence, modulation of immune system activity, remodeling of the extracellular matrix, alteration of tissue structure, and promotion of cancer progression. Identifying key factors within the SASP is crucial for understanding the underlying mechanisms of senescence and developing effective strategies to counteract cellular senescence. Our research has specifically focused on investigating the role of IGFBP5, a component of the SASP observed in various experimental models and conditions.Through our studies, we have demonstrated that IGFBP5 actively contributes to promoting senescence and can induce senescence in neighboring cells. We have gained valuable insights into the mechanisms through which IGFBP5 exerts its pro-senescence effects. These mechanisms include its release following genotoxic stress, involvement in signaling pathways mediated by reactive oxygen species and prostaglandins, internalization via specialized structures called caveolae, and interaction with a specific protein known as RARα. By uncovering these mechanisms, we have advanced our understanding of the intricate role of IGFBP5 in the senescence process. The significance of IGFBP5 as a pro-aging factor stems from an in vivo study we conducted on patients undergoing Computer Tomography analysis. In these patients, we observed an elevation in circulating IGFBP5 levels in response to radiation-induced organismal stress.Globally, our findings highlight the potential of IGFBP5 as a promising therapeutic target for age-related diseases and cancer.

A two-kinesin mechanism controls neurogenesis in the developing brain

During the course of brain development, Radial Glial Progenitor (RGP) cells give rise to most of the neurons required for a functional cortex. RGPs can undergo symmetric divisions, which result in RGP duplication, or asymmetric divisions, which result in one RGP as well as one to four neurons. The control of this balance is not fully understood, but must be closely regulated to produce the cells required for a functioning cortex, and to maintain the stem cell pool. In this study, we show that the balance between symmetric and asymmetric RGP divisions is in part regulated by the actions of two kinesins, Kif1A and Kif13B, which we find have opposing roles in neurogenesis through their action on the mitotic spindle in dividing RGPs. We find that Kif1A promotes neurogenesis, whereas Kif13B promotes symmetric, non-neurogenic divisions. Interestingly, the two kinesins are closely related in structure, and members of the same kinesin-3 subfamily, thus their opposing effects on spindle orientation appear to represent a novel mechanism for the regulation of neurogenesis.

Control of motor landing and processivity by the CAP-Gly domain in the KIF13B tail

Microtubules are major components of the eukaryotic cytoskeleton. Posttranslational modifications (PTMs) of tubulin regulates interactions with microtubule-associated proteins (MAPs). One unique PTM is the cyclical removal and re-addition of the C-terminal tyrosine of α-tubulin and MAPs containing CAP-Gly domains specifically recognize tyrosinated microtubules. KIF13B, a long-distance transport kinesin, contains a conserved CAP-Gly domain, but the role of the CAP-Gly domain in KIF13B's motility along microtubules remains unknown. To address this, we investigate the interaction between KIF13B's CAP-Gly domain, and tyrosinated microtubules. We find that KIF13B's CAP-Gly domain influences the initial motor-microtubule interaction, as well as processive motility along microtubules. The effect of the CAP-Gly domain is enhanced when the motor domain is in the ADP state, suggesting an interplay between the N-terminal motor domain and C-terminal CAP-Gly domain. These results reveal that specialized kinesin tail domains play active roles in the initiation and continuation of motor movement.

Lipid-Based Nanocarriers in the Treatment of Glioblastoma Multiforme (GBM): Challenges and Opportunities

Glioblastoma multiforme (also known as glioblastoma; GBM) is one of the most malignant types of brain tumors that occurs in the CNS. Treatment strategies for glioblastoma are majorly comprised of surgical resection, radiotherapy, and chemotherapy along with combination therapy. Treatment of GBM is itself a tedious task but the involved barriers in GBM are one of the main impediments to move one step closer to the treatment of GBM. Basically, two of the barriers are of utmost importance in this regard, namely blood brain barrier (BBB) and blood brain tumor barrier (BBTB). This review will address different challenges and barriers in the treatment of GBM along with their etiology. The role and recent progress of lipid-based nanocarriers like liposomes, solid lipid nanocarriers (SLNs), nanostructured lipid carriers (NLCs), lipoplexes, and lipid hybrid carriers in the effective management of GBM will be discussed in detail.

KIF13B mediates VEGFR2 recycling to modulate vascular permeability

Excessive vascular endothelial growth factor-A (VEGF-A) signaling induces vascular leakage and angiogenesis in diseases. VEGFR2 trafficking to the cell surface, mediated by kinesin-3 family protein KIF13B, is essential to respond to VEGF-A when inducing angiogenesis. However, the precise mechanism of how KIF13B regulates VEGF-induced signaling and its effects on endothelial permeability is largely unknown. Here we show that KIF13B-mediated recycling of internalized VEGFR2 through Rab11-positive recycling vesicle regulates endothelial permeability. Phosphorylated VEGFR2 at the cell-cell junction was internalized and associated with KIF13B in Rab5-positive early endosomes. KIF13B mediated VEGFR2 recycling through Rab11-positive recycling vesicle. Inhibition of the function of KIF13B attenuated phosphorylation of VEGFR2 at Y951, SRC at Y416, and VE-cadherin at Y685, which are necessary for endothelial permeability. Failure of VEGFR2 trafficking to the cell surface induced accumulation and degradation of VEGFR2 in lysosomes. Furthermore, in the animal model of the blinding eye disease wet age-related macular degeneration (AMD), inhibition of KIF13B-mediated VEGFR2 trafficking also mitigated vascular leakage. Thus, the present results identify the fundamental role of VEGFR2 recycling to the cell surface in mediating vascular permeability, which suggests a promising strategy for mitigating vascular leakage associated with inflammatory diseases.

Spatio-Temporal Expression Pattern of CAKUT Candidate Genes DLG1 and KIF12 during Human Kidney Development

We aimed to investigate expression of the novel susceptibility genes for CAKUT, DLG1 and KIF12, proposed by a systematic in silico approach, in developing and postnatal healthy human kidneys to provide information about their spatiotemporal expression pattern. We analyzed expression of their protein products by immunohistochemistry and immunofluorescence and quantified relative mRNA levels by RT-qPCR. Statistically significant differences in expression patterns were observed between certain developmental stages. Strong expression of DLG1 was observed in the developing kidney, with a gradual decrease from the first phase of kidney development (Ph1) until the third phase (Ph3), when most nephrons are formed; at later stages, the highest expression was observed in the tubules. KIF12 was highly expressed in the developing structures, especially in Ph1, with a gradual decrease until the postnatal phase, which would indicate a significant role in nephrogenesis. Co-localization of DLG1 and KIF12 was pronounced in Ph1, especially on the apical side of the tubular epithelial cells. Thereafter, their expression gradually became weaker and was only visible as punctate staining in Ph4. The direct association of DLG1 with KIF12 as control genes of normal kidney development may reveal their new functional aspect in renal tubular epithelial cells.

KIF1A-Associated Neurological Disorder: An Overview of a Rare Mutational Disease

KIF1A-associated neurological diseases (KANDs) are a group of inherited conditions caused by changes in the microtubule (MT) motor protein KIF1A as a result of KIF1A gene mutations. Anterograde transport of membrane organelles is facilitated by the kinesin family protein encoded by the MT-based motor gene KIF1A. Variations in the KIF1A gene, which primarily affect the motor domain, disrupt its ability to transport synaptic vesicles containing synaptophysin and synaptotagmin leading to various neurological pathologies such as hereditary sensory neuropathy, autosomal dominant and recessive forms of spastic paraplegia, and different neurological conditions. These mutations are frequently misdiagnosed because they result from spontaneous, non-inherited genomic alterations. Whole-exome sequencing (WES), a cutting-edge method, assists neurologists in diagnosing the illness and in planning and choosing the best course of action. These conditions are simple to be identified in pediatric and have a life expectancy of 5-7 years. There is presently no permanent treatment for these illnesses, and researchers have not yet discovered a medicine to treat them. Scientists have more hope in gene therapy since it can be used to cure diseases brought on by mutations. In this review article, we discussed some of the experimental gene therapy methods, including gene replacement, gene knockdown, symptomatic gene therapy, and cell suicide gene therapy. It also covered its clinical symptoms, pathogenesis, current diagnostics, therapy, and research advances currently occurring in the field of KAND-related disorders. This review also explained the impact that gene therapy can be designed in this direction and afford the remarkable benefits to the patients and society.

Postprandial triglyceride-rich lipoproteins promote the adipogenic differentiation of adipose-derived mesenchymal stem cells via the LRP1/caveolin-1/AKT1 pathway

Diet-induced obesity (OB) is usually accompanied by hypertriglyceridemia, which is characterized by the accumulation of triglyceride (TG)-rich lipoprotein (TRL) particles in the circulation. We previously found that postprandial TRL combined with insulin induced the adipogenic differentiation of 3T3-L1 preadipocytes, which may represent a key mechanism underlying obesity. However, the specific mechanism and signaling pathway involved in this process remain to be fully elucidated. In this study, we found that, in the postprandial state, patients with obesity had significantly higher levels of TG and remnant cholesterol (RC) than normal-weight controls. In vitro, we found that postprandial TRL, together with insulin, promoted the adipogenic differentiation of adipose-derived mesenchymal stem cells (AMSCs), as evidenced by the increased expression of lipogenesis-related genes and their protein products, including low-density lipoprotein related protein 1 (LRP1). Besides, caveolin-1 (Cav-1) expression was also significantly upregulated under this condition. Cav-1 and LRP1 were observed to interact, and then led to the activation of the PI3K/AKT1 signaling pathway. Meanwhile, the inhibition of LRP1 or Cav-1 significantly attenuated the adipogenic differentiation of AMSCs and downregulated AKT1 phosphorylation levels. Moreover, treatment with a selective AKT1 inhibitor significantly suppressed postprandial TRL and insulin-induced adipogenesis in AMSCs. Combined, our results demonstrated that, in association with insulin, postprandial TRL can promote the adipogenic differentiation of AMSCs in a manner that is dependent on the LRP1/Cav-1-mediated activation of the PI3K/AKT1 signaling pathway. Our findings indicated that a postprandial increase in TRL content is a critical factor in the pathogenesis of hypertriglyceridemia and diet-induced obesity.

PI4P and BLOC-1 remodel endosomal membranes into tubules

Intracellular trafficking is mediated by transport carriers that originate by membrane remodeling from donor organelles. Tubular carriers contribute to the flux of membrane lipids and proteins to acceptor organelles, but how lipids and proteins impose a tubular geometry on the carriers is incompletely understood. Using imaging approaches on cells and in vitro membrane systems, we show that phosphatidylinositol-4-phosphate (PI4P) and biogenesis of lysosome-related organelles complex 1 (BLOC-1) govern the formation, stability, and functions of recycling endosomal tubules. In vitro, BLOC-1 binds and tubulates negatively charged membranes, including those containing PI4P. In cells, endosomal PI4P production by type II PI4-kinases is needed to form and stabilize BLOC-1-dependent recycling endosomal tubules. Decreased PI4KIIs expression impairs the recycling of endosomal cargoes and the life cycles of intracellular pathogens such as Chlamydia bacteria and influenza virus that exploit the membrane dynamics of recycling endosomes. This study demonstrates how a phospholipid and a protein complex coordinate the remodeling of cellular membranes into functional tubules.

Angiomotin isoform 2 promotes binding of PALS1 to KIF13B at primary cilia and regulates ciliary length and signaling

The kinesin-3 motor KIF13B functions in endocytosis, vesicle transport and regulation of ciliary length and signaling. Direct binding of the membrane-associated guanylate kinase (MAGUK) DLG1 to the MAGUK-binding stalk domain of KIF13B relieves motor autoinhibition and promotes microtubule plus-end-directed cargo transport. Here, we characterize angiomotin (AMOT) isoform 2 (p80, referred to as Ap80) as a novel KIF13B interactor that promotes binding of another MAGUK, the polarity protein and Crumbs complex component PALS1, to KIF13B. Live-cell imaging analysis indicated that Ap80 is concentrated at and recruits PALS1 to the base of the primary cilium, but is not a cargo of KIF13B itself. Consistent with a ciliary function for Ap80, its depletion led to elongated primary cilia and reduced agonist-induced ciliary accumulation of SMO, a key component of the Hedgehog signaling pathway, whereas Ap80 overexpression caused ciliary shortening. Our results suggest that Ap80 activates KIF13B cargo binding at the base of the primary cilium to regulate ciliary length, composition and signaling.

Kinesins in Mammalian Spermatogenesis and Germ Cell Transport

In mammalian testes, the apical cytoplasm of each Sertoli cell holds up to several dozens of germ cells, especially spermatids that are transported up and down the seminiferous epithelium. The blood-testis barrier (BTB) established by neighboring Sertoli cells in the basal compartment restructures on a regular basis to allow preleptotene/leptotene spermatocytes to pass through. The timely transfer of germ cells and other cellular organelles such as residual bodies, phagosomes, and lysosomes across the epithelium to facilitate spermatogenesis is important and requires the microtubule-based cytoskeleton in Sertoli cells. Kinesins, a superfamily of the microtubule-dependent motor proteins, are abundantly and preferentially expressed in the testis, but their functions are poorly understood. This review summarizes recent findings on kinesins in mammalian spermatogenesis, highlighting their potential role in germ cell traversing through the BTB and the remodeling of Sertoli cell-spermatid junctions to advance spermatid transport. The possibility of kinesins acting as a mediator and/or synchronizer for cell cycle progression, germ cell transit, and junctional rearrangement and turnover is also discussed. We mostly cover findings in rodents, but we also make special remarks regarding humans. We anticipate that this information will provide a framework for future research in the field.

Interaction of surfactant coated PLGA nanoparticles with in vitro human brain-like endothelial cells

Treatment for CNS related diseases are limited by the difficulty of the drugs to cross the blood-brain barrier (BBB). The functionalization of polymeric nanoparticles (NPs) coated with the surfactants polysorbate 80 (PS80) and poloxamer 188 (P188), have shown promising results as drugs carriers are able to cross the BBB on animal models. In this study, poly(lactide-co-glycolide) (PLGA) NPs coated with PS80 and P188, labelled with a fluorescent dye were tested on human pre-clinical in vitro model to evaluate and compare their uptake profiles, mechanisms of transport and crossing over human brain-like endothelial cells (BLECs) mimicking the human BBB. In addition, these NPs were produced using a method facilitating their reproducible production at high scale, the MicroJet reactor® technology. Results showed that both formulations were biocompatible and able to be internalized within the BLECs in different uptake profiles depending on their coating: P188 NP showed higher internalization capacity than PS80 NP. Both NPs uptakes were ATP-dependent, following more than one endocytosis pathway with colocalization in the early endosomes, ending with a NPs release in the brain compartment. Thus, both surfactant-coated PLGA NPs are interesting formulations for delivery to the brain through the BBB, presenting different uptake profiles.

KIF13B-mediated VEGFR2 trafficking is essential for vascular leakage and metastasis in vivo

VEGF-A induces vascular leakage and angiogenesis via activating the cell surface localized receptor VEGF receptor 2 (VEGFR2). The amount of available VEGFR2 at the cell surface is however tightly regulated by trafficking of VEGFR2 by kinesin family 13 B (KIF13B), a plus-end kinesin motor, to the plasma membrane of endothelial cells (ECs). Competitive inhibition of interaction between VEGFR2 and KIF13B by a peptide kinesin-derived angiogenesis inhibitor (KAI) prevented pathological angiogenesis in models of cancer and eye disease associated with defective angiogenesis. Here, we show the protective effects of KAI in VEGF-A-induced vascular leakage and cancer metastasis. Using an EC-specific KIF13B knockout (Kif13b iECKO ) mouse model, we demonstrated the function of EC expressed KIF13B in mediating VEGF-A-induced vascular leakage, angiogenesis, tumor growth, and cancer metastasis. Thus, KIF13B-mediated trafficking of VEGFR2 to the endothelial surface has an essential role in pathological angiogenesis induced by VEGF-A, and is therefore a potential therapeutic target.

Motor domain-mediated autoinhibition dictates axonal transport by the kinesin UNC-104/KIF1A

The UNC-104/KIF1A motor is crucial for axonal transport of synaptic vesicles, but how the UNC-104/KIF1A motor is activated in vivo is not fully understood. Here, we identified point mutations located in the motor domain or the inhibitory CC1 domain, which resulted in gain-of-function alleles of unc-104 that exhibit hyperactive axonal transport and abnormal accumulation of synaptic vesicles. In contrast to the cell body localization of wild type motor, the mutant motors accumulate on neuronal processes. Once on the neuronal process, the mutant motors display dynamic movement similarly to wild type motors. The gain-of-function mutation on the motor domain leads to an active dimeric conformation, releasing the inhibitory CC1 region from the motor domain. Genetically engineered mutations in the motor domain or CC1 of UNC-104, which disrupt the autoinhibitory interface, also led to the gain of function and hyperactivation of axonal transport. Thus, the CC1/motor domain-mediated autoinhibition is crucial for UNC-104/KIF1A-mediated axonal transport in vivo.

UNC-104/KIF1A is the founding member of the kinesin-3 family. When not transporting cargos, most kinesin-3 motors adopt an autoinhibited conformation, and how the UNC-104/KIF1A motor is activated in vivo is not fully understood. Here, we identified gain-of-function mutations in the motor domain or CC1 domain that significantly enhance the synaptic vesicle transport. Further biochemical and structural analyses revealed that these mutations could disrupt the CC1/motor mediated autoinhibition. Thus, our work provides a mechanistic explanation for the role of some disease-related mutations in motor hyperactivation.

VEGFR2 Trafficking by KIF13B Is a Novel Therapeutic Target for Wet Age-Related Macular Degeneration

Purpose

Vascular endothelial growth factor (VEGF) and its receptor VEGFR2 are promising therapeutic targets for wet age-related macular degeneration (AMD). As a topically applicable option, we developed the peptide KAI to selectively interfere with VEGFR2 trafficking to the cell surface where it receives VEGF. This study sought to determine the efficacy of KAI in the mouse model of choroidal neovascularization (CNV).

Methods

The specificity of KAI was tested by surface plasmon resonance. The drug delivery was analyzed by cryosection and the ELISA after treatment of KAI eyedrop to the mouse eyes. For the laser-induced CNV model, mice with laser-induced ruptures in Bruch's membrane received daily treatment of KAI eyedrop or control peptide. The other groups of mice received intravitreal injection of anti-VEGF or IgG control. After two weeks, CNV was quantified and compared.

Results

First, we showed the specificity and high affinity of KAI to VEGFR2. Next, biodistribution revealed successful delivery of KAI eyedrop to the back of the mouse eyes. KAI significantly reduced the disease progression in laser-induced CNV. The comparison with current therapy suggests that KAI eyedrop is as effective as current therapy to prevent CNV in wet AMD. Moreover, the genetic deletion of a kinesin KIF13B, which mediates VEGFR2 trafficking to the cell surface, confirmed the pivotal role of KIF13B in disease progression of wet AMD and neovascularization from choroidal vessels.

Conclusions

Taken together, pharmacologic inhibition and genetic deletion complementarily suggest the therapeutic possibility of targeting VEGFR2 trafficking to inhibit pathological angiogenesis in wet AMD.

The developmental biology of kinesins

Kinesins are microtubule-based motor proteins that are well known for their key roles in cell biological processes ranging from cell division, to intracellular transport of mRNAs, proteins, vesicles, and organelles, and microtubule disassembly. Interestingly, many of the ~45 distinct kinesin genes in vertebrate genomes have also been associated with specific phenotypes in embryonic development. In this review, we highlight the specific developmental roles of kinesins, link these to cellular roles reported in vitro, and highlight remaining gaps in our understanding of how this large and important family of proteins contributes to the development and morphogenesis of animals.

A Role for Caveolin-3 in the Pathogenesis of Muscular Dystrophies

Caveolae are the cholesterol-rich small invaginations of the plasma membrane present in many cell types including adipocytes, endothelial cells, epithelial cells, fibroblasts, smooth muscles, skeletal muscles and cardiac muscles. They serve as specialized platforms for many signaling molecules and regulate important cellular processes like energy metabolism, lipid metabolism, mitochondria homeostasis, and mechano-transduction. Caveolae can be internalized together with associated cargo. The caveolae-dependent endocytic pathway plays a role in the withdrawal of many plasma membrane components that can be sent for degradation or recycled back to the cell surface. Caveolae are formed by oligomerization of caveolin proteins. Caveolin-3 is a muscle-specific isoform, whose malfunction is associated with several diseases including diabetes, cancer, atherosclerosis, and cardiovascular diseases. Mutations in Caveolin-3 are known to cause muscular dystrophies that are collectively called caveolinopathies. Altered expression of Caveolin-3 is also observed in Duchenne’s muscular dystrophy, which is likely a part of the pathological process leading to muscle weakness. This review summarizes the major functions of Caveolin-3 in skeletal muscles and discusses its involvement in the pathology of muscular dystrophies.

Lung Endothelial Transcytosis

Transcytosis of macromolecules through lung endothelial cells is the primary route of transport from the vascular compartment into the interstitial space. Endothelial transcytosis is mostly a caveolae-dependent process that combines receptor-mediated endocytosis, vesicle trafficking via actin-cytoskeletal remodeling, and SNARE protein directed vesicle fusion and exocytosis. Herein, we review the current literature on caveolae-mediated endocytosis, the role of actin cytoskeleton in caveolae stabilization at the plasma membrane, actin remodeling during vesicle trafficking, and exocytosis of caveolar vesicles. Next, we provide a concise summary of experimental methods employed to assess transcytosis. Finally, we review evidence that transcytosis contributes to the pathogenesis of acute lung injury. © 2020 American Physiological Society. Compr Physiol 10:491-508, 2020.

Regulation of the Extracellular Matrix by Ciliary Machinery

The primary cilium is an organelle involved in cellular signalling. Mutations affecting proteins involved in cilia assembly or function result in diseases known as ciliopathies, which cause a wide variety of phenotypes across multiple tissues. These mutations disrupt various cellular processes, including regulation of the extracellular matrix. The matrix is important for maintaining tissue homeostasis through influencing cell behaviour and providing structural support; therefore, the matrix changes observed in ciliopathies have been implicated in the pathogenesis of these diseases. Whilst many studies have associated the cilium with processes that regulate the matrix, exactly how these matrix changes arise is not well characterised. This review aims to bring together the direct and indirect evidence for ciliary regulation of matrix, in order to summarise the possible mechanisms by which the ciliary machinery could regulate the composition, secretion, remodelling and organisation of the matrix.

Intraperitoneal dye injection method for visualizing the functioning lymphatic vascular system in zebrafish and medaka

A hierarchically organized lymphatic vascular system extends throughout the vertebrate body for tissue fluid homeostasis, immune trafficking, and the absorption of dietary fats. Intralymphatic dye injection and serial sectioning have been the main tools for visualizing lymphatic vessels. Specific markers for identifying the lymphatic vasculature in zebrafish and medaka have appeared as new tools that enable the study of lymphangiogenesis using genetic and experimental manipulation. Transgenic fishes have become excellent organisms for visualizing the lymphatic vasculature in living embryos, but this method has limited usefulness, especially in later developmental stages. The functional lymphatic endothelium predominantly takes up foreign particles in zebrafish and medaka. We utilized this physiological activity and lymph flow to label lymphatic vessels. Intraperitoneal injection of trypan blue is useful for temporal observations of the lymphatic ducts, which are essential for large-scale genetic screening, while cinnabar (HgS) injection allows identification of the lymphatic endothelium under electron microscopy, avoiding artefactual damage. This injection method, which is not high in cost and does not require high skill or special devices, is applicable to any live fish with functioning lymphatic vessels, even mutants, with high reproducibility for visualizing the entire lymphatic vascular system.

Myeloid-Specific Deletion of Epsins 1 and 2 Reduces Atherosclerosis by Preventing LRP-1 Downregulation

RATIONALE

Atherosclerosis is, in part, caused by immune and inflammatory cell infiltration into the vascular wall, leading to enhanced inflammation and lipid accumulation in the aortic endothelium. Understanding the molecular mechanisms underlying this disease is critical for the development of new therapies. Our recent studies demonstrate that epsins, a family of ubiquitin-binding endocytic adaptors, are critical regulators of atherogenicity. Given the fundamental contribution lesion macrophages make to fuel atherosclerosis, whether and how myeloid-specific epsins promote atherogenesis is an open and significant question.

OBJECTIVE

We will determine the role of myeloid-specific epsins in regulating lesion macrophage function during atherosclerosis.

METHODS AND RESULTS

We engineered myeloid cell-specific epsins double knockout mice (LysM-DKO) on an ApoE^-/- background. On Western diet, these mice exhibited marked decrease in atherosclerotic lesion formation, diminished immune and inflammatory cell content in aortas, and reduced necrotic core content but increased smooth muscle cell content in aortic root sections. Epsins deficiency hindered foam cell formation and suppressed proinflammatory macrophage phenotype but increased efferocytosis and anti-inflammatory macrophage phenotype in primary macrophages. Mechanistically, we show that epsin loss specifically increased total and surface levels of LRP-1 (LDLR [low-density lipoprotein receptor]-related protein 1), an efferocytosis receptor with antiatherosclerotic properties. We further show that epsin and LRP-1 interact via epsin's ubiquitin-interacting motif domain. ox-LDL (oxidized LDL) treatment increased LRP-1 ubiquitination, subsequent binding to epsin, and its internalization from the cell surface, suggesting that epsins promote the ubiquitin-dependent internalization and downregulation of LRP-1. Crossing ApoE^-/-/LysM-DKO mice onto an LRP-1 heterozygous background restored, in part, atherosclerosis, suggesting that epsin-mediated LRP-1 downregulation in macrophages plays a pivotal role in propelling atherogenesis.

CONCLUSIONS

Myeloid epsins promote atherogenesis by facilitating proinflammatory macrophage recruitment and inhibiting efferocytosis in part by downregulating LRP-1, implicating that targeting epsins in macrophages may serve as a novel therapeutic strategy to treat atherosclerosis.

LDL receptor related protein 1 requires the I3 domain of discs-large homolog 1/DLG1 for interaction with the kinesin motor protein KIF13B

KIF13B, a kinesin-3 family motor, was originally identified as GAKIN due to its biochemical interaction with human homolog of Drosophila discs-large tumor suppressor (hDLG1). Unlike its homolog KIF13A, KIF13B contains a carboxyl-terminal CAP-Gly domain. To investigate the function of the CAP-Gly domain, we developed a mouse model that expresses a truncated form of KIF13B protein lacking its CAP-Gly domain (KIF13BΔCG), whereas a second mouse model lacks the full-length KIF13A. Here we show that the KIF13BΔCG mice exhibit relatively higher serum cholesterol consistent with the reduced uptake of [³H]CO-LDL in KIF13BΔCG mouse embryo fibroblasts. The plasma level of factor VIII was not significantly elevated in the KIF13BΔCG mice, suggesting that the CAP-Gly domain region of KIF13B selectively regulates LRP1-mediated lipoprotein endocytosis. No elevation of either serum cholesterol or plasma factor VIII was observed in the full length KIF13A null mouse model. The deletion of the CAP-Gly domain region caused subcellular mislocalization of truncated KIF13B concomitant with the mislocalization of LRP1. Mechanistically, the cytoplasmic domain of LRP1 interacts specifically with the alternatively spliced I₃ domain of DLG1, which complexes with KIF13B via their GUK-MBS domains, respectively. Importantly, double mutant mice generated by crossing KIF13A null and KIF13BΔCG mice suffer from perinatal lethality showing potential craniofacial defects. Together, this study provides first evidence that the carboxyl-terminal region of KIF13B containing the CAP-Gly domain is important for the LRP1-DLG1-KIF13B complex formation with implications in the regulation of metabolism, cell polarity, and development.

WHAMM initiates autolysosome tubulation by promoting actin polymerization on autolysosomes

WHAMM, a member of the Wiskott-Aldrich syndrome protein (WASP) family, is an actin nucleation promoting factor (NPF) that also associates with membranes and microtubules. Here we report that WHAMM is required for autophagic lysosome reformation (ALR). WHAMM knockout causes impairment of autolysosome tubulation, which results in accumulation of enlarged autolysosomes during prolonged starvation. Mechanistically, WHAMM is recruited to the autolysosome membrane through its specific interaction with PI(4,5)P₂. WHAMM then works as an NPF which promotes assembly of an actin scaffold on the surface of the autolysosome to promote autolysosome tubulation. Our study demonstrates an unexpected role of the actin scaffold in regulating autophagic lysosome reformation.

After autophagic cargo degradation, autolysosomes undergo a reformation process to recycle lysosomal membrane components. Here, Dai et al. demonstrate that the actin nucleation promoting factor WHAMM is required for autolysosome reformation by providing an actin scaffold to drive tubulation.

Low Density Receptor-Related Protein 1 Interactions With the Extracellular Matrix: More Than Meets the Eye

The extracellular matrix (ECM) is a biological substrate composed of collagens, proteoglycans and glycoproteins that ensures proper cell migration and adhesion and keeps the cell architecture intact. The regulation of the ECM composition is a vital process strictly controlled by, among others, proteases, growth factors and adhesion receptors. As it appears, ECM remodeling is also essential for proper neuronal and glial development and the establishment of adequate synaptic signaling. Hence, disturbances in ECM functioning are often present in neurodegenerative diseases like Alzheimer’s disease. Moreover, mutations in ECM molecules are found in some forms of epilepsy and malfunctioning of ECM-related genes and pathways can be seen in, for example, cancer or ischemic injury. Low density lipoprotein receptor-related protein 1 (Lrp1) is a member of the low density lipoprotein receptor family. Lrp1 is involved not only in ligand uptake, receptor mediated endocytosis and lipoprotein transport—functions shared by low density lipoprotein receptor family members—but also regulates cell surface protease activity, controls cellular entry and binding of toxins and viruses, protects against atherosclerosis and acts on many cell signaling pathways. Given the plethora of functions, it is not surprising that Lrp1 also impacts the ECM and is involved in its remodeling. This review focuses on the role of Lrp1 and some of its major ligands on ECM function. Specifically, interactions with two Lrp1 ligands, integrins and tissue plasminogen activator are described in more detail.

Dual complementary liposomes inhibit triple-negative breast tumor progression and metastasis

Distinguishing malignant cells from non-neoplastic ones is a major challenge in triple-negative breast cancer (TNBC) treatment. Here, we developed a complementary targeting strategy that uses precisely matched, multivalent ligand-receptor interactions to recognize and target TNBC tumors at the primary site and metastatic lesions. We screened a panel of cancer cell surface markers and identified intercellular adhesion molecule-1 (ICAM1) and epithelial growth factor receptor (EGFR) as optimal candidates for TNBC complementary targeting. We engineered a dual complementary liposome (DCL) that precisely complements the molecular ratio and organization of ICAM1 and EGFR specific to TNBC cell surfaces. Our in vitro mechanistic studies demonstrated that DCLs, compared to single-targeting liposomes, exhibited increased binding, enhanced internalization, and decreased receptor signaling. DCLs consistently exhibited substantially increased tumor targeting activity and antitumor efficacy in orthotopic and lung metastasis models, indicating that DCLs are a platform technology for the design of personalized nanomedicines for TNBC.

Ciliary kinesins beyond IFT: Cilium length, disassembly, cargo transport and signalling

Cilia and flagella are microtubule-based antenna which are highly conserved among eukaryotes. In vertebrates, primary and motile cilia have evolved to exert several key functions during development and tissue homoeostasis. Ciliary dysfunction in humans causes a highly heterogeneous group of diseases called ciliopathies, a class of genetic multisystemic disorders primarily affecting kidney, skeleton, retina, lung and the central nervous system. Among key ciliary proteins, kinesin family members (KIF) are microtubule-interacting proteins involved in many diverse cellular functions, including transport of cargo (organelles, proteins and lipids) along microtubules and regulating the dynamics of cytoplasmic and spindle microtubules through their depolymerising activity. Many KIFs are also involved in diverse ciliary functions including assembly/disassembly, motility and signalling. We here review these ciliary kinesins in vertebrates and focus on their involvement in ciliopathy-related disorders.

Plasma proteome correlates of lipid and lipoprotein: biomarkers of metabolic diversity and inflammation in children of rural Nepal

Proteins involved in lipoprotein metabolism can modulate cardiovascular health. While often measured to assess adult metabolic diseases, little is known about the proteomes of lipoproteins and their relation to metabolic dysregulation and underlying inflammation in undernourished child populations. The objective of this population study was to globally characterize plasma proteins systemically associated with HDL, LDL, and triglycerides in 500 Nepalese children. Abnormal lipid profiles characterized by elevated plasma triglycerides and low HDL-cholesterol (HDL-C) concentrations were common, especially in children with subclinical inflammation. Among 982 proteins analyzed, the relative abundance of 11, 12, and 52 plasma proteins was correlated with LDL-cholesterol (r = −0.43∼0.70), triglycerides (r = −0.39∼0.53), and HDL-C (r = −0.49∼0.79) concentrations, respectively. These proteins included apolipoproteins and numerous unexpected intracellular and extracellular matrix binding proteins, likely originating in hepatic and peripheral tissues. Relative abundance of two-thirds of the HDL proteome varied with inflammation, with acute phase reactants higher by 4∼40%, and proteins involved in HDL biosynthesis, cholesterol efflux, vitamin transport, angiogenesis, and tissue repair lower by 3∼20%. Untargeted plasma proteomics detects comprehensive sets of both known and novel lipoprotein-associated proteins likely reflecting systemic regulation of lipoprotein metabolism and vascular homeostasis. Inflammation-altered distributions of the HDL proteome may be predisposing undernourished populations to early chronic disease.

Coiled-coil 1-mediated fastening of the neck and motor domains for kinesin-3 autoinhibition

In kinesin-3, the coiled-coil 1 (CC1) can sequester the preceding neck coil (NC) for autoinhibition, but the underlying mechanism is poorly understood. Here, we determined the structures of the uninhibited motor domain (MD)-NC dimer and inhibited MD-NC-CC1 monomer of kinesin-3 KIF13B. In the MD-NC-CC1 monomer, CC1 is broken into two short helices that unexpectedly interact with both the NC and the MD. Compared with the MD-NC dimer, the CC1-mediated integration of NC and MD not only blocks the NC dimer formation, but also prevents the neck linker (NL) undocking and the ADP release from the MD. Mutations of the essential residues in the interdomain interaction interface in the MD-NC-CC1 monomer restored the MD activity. Thus, CC1 fastens the neck domain and MD and inhibits both NC and NL. This CC1-mediated lockdown of the entire neck domain may represent a paradigm for kinesin autoinhibition that could be applicable to other kinesin-3 motors.

Regulation of ciliary membrane protein trafficking and signalling by kinesin motor proteins

Primary cilia are antenna-like sensory organelles that regulate a substantial number of cellular signalling pathways in vertebrates, both during embryonic development as well as in adulthood, and mutations in genes coding for ciliary proteins are causative of an expanding group of pleiotropic diseases known as ciliopathies. Cilia consist of a microtubule-based axoneme core, which is subtended by a basal body and covered by a bilayer lipid membrane of unique protein and lipid composition. Cilia are dynamic organelles, and the ability of cells to regulate ciliary protein and lipid content in response to specific cellular and environmental cues is crucial for balancing ciliary signalling output. Here we discuss mechanisms involved in regulation of ciliary membrane protein trafficking and signalling, with main focus on kinesin-2 and kinesin-3 family members.

Cilia protein IFT88 regulates extracellular protease activity by optimizing LRP-1-mediated endocytosis

Matrix protease activity is fundamental to developmental tissue patterning and remains influential in adult homeostasis. In cartilage, the principal matrix proteoglycan is aggrecan, the protease-mediated catabolism of which defines arthritis; however, the pathophysiologic mechanisms that drive aberrant aggrecanolytic activity remain unclear. Human ciliopathies exhibit altered matrix, which has been proposed to be the result of dysregulated hedgehog signaling that is tuned within the primary cilium. Here, we report that disruption of intraflagellar transport protein 88 (IFT88), a core ciliary trafficking protein, increases chondrocyte aggrecanase activity in vitro. We find that the receptor for protease endocytosis in chondrocytes, LDL receptor-related protein 1 (LRP-1), is unevenly distributed over the cell membrane, often concentrated at the site of cilia assembly. Hypomorphic mutation of IFT88 disturbs this apparent hot spot for protease uptake, increases receptor shedding, and results in a reduced rate of protease clearance from the extracellular space. We propose that IFT88 and/or the cilium regulates the extracellular remodeling of matrix-independently of Hedgehog regulation-by enabling rapid LRP-1-mediated endocytosis of proteases, potentially by supporting the creation of a ciliary pocket. This result highlights new roles for the cilium's machinery in matrix turnover and LRP-1 function, with potential relevance in a range of diseases.-Coveney, C. R., Collins, I., Mc Fie, M., Chanalaris, A., Yamamoto, K., Wann, A. K. T. Cilia protein IFT88 regulates extracellular protease activity by optimizing LRP-1-mediated endocytosis.

Kinesin Khc-73/KIF13B modulates retrograde BMP signaling by influencing endosomal dynamics at the Drosophila neuromuscular junction

Retrograde signaling is essential for neuronal growth, function and survival; however, we know little about how signaling endosomes might be directed from synaptic terminals onto retrograde axonal pathways. We have identified Khc-73, a plus-end directed microtubule motor protein, as a regulator of sorting of endosomes in Drosophila larval motor neurons. The number of synaptic boutons and the amount of neurotransmitter release at the Khc-73 mutant larval neuromuscular junction (NMJ) are normal, but we find a significant decrease in the number of presynaptic release sites. This defect in Khc-73 mutant larvae can be genetically enhanced by a partial genetic loss of Bone Morphogenic Protein (BMP) signaling or suppressed by activation of BMP signaling in motoneurons. Consistently, activation of BMP signaling that normally enhances the accumulation of phosphorylated form of BMP transcription factor Mad in the nuclei, can be suppressed by genetic removal of Khc-73. Using a number of assays including live imaging in larval motor neurons, we show that loss of Khc-73 curbs the ability of retrograde-bound endosomes to leave the synaptic area and join the retrograde axonal pathway. Our findings identify Khc-73 as a regulator of endosomal traffic at the synapse and modulator of retrograde BMP signaling in motoneurons.

High Concentrations of Rosiglitazone Reduce mRNA and Protein Levels of LRP1 in HepG2 Cells

Low-density lipoprotein receptor-related protein 1 (LRP1) is an endocytic receptor involved in the uptake of a variety of molecules, such as apoE, α2-macroglobulin, and the amyloid β peptide (Aβ), for either transcellular transport, protein trafficking or lysosomal degradation. The LRP1 gene can be transcribed upon activation of peroxisome proliferator receptor activated-γ (PPARγ) by the potent PPARγ agonist, rosiglitazone (RGZ). In previous studies, RGZ was shown to upregulate LRP1 levels in concentrations between 0.1 and 5 μM in HepG2 cells. In this study, we sought to replicate previous studies and to investigate the molecular mechanism by which high concentrations of RGZ reduce LRP1 levels in HepG2 cells. Our data confirmed that transcriptional activation of LRP1 occurred in response to RGZ at 3 and 10 μM, in agreement with the study reported by Moon et al. (2012a). On the other hand, we found that high concentrations of RGZ decreased both mRNA and protein levels of LRP1. Mechanistically, transcriptional dysregulation of LRP1 was affected by the downregulation of PPARγ in a time- and concentration-dependent manner. However, downregulation of PPARγ was responsible for only 40% of the LRP1 reduction and thereby the remaining loss of LRP1 (60%) was found to be through degradation in the lysosomal system. In conclusion, our findings demonstrate the mechanisms by which high concentrations of RGZ caused LRP1 levels to be reduced in HepG2 cells. Taken together, this data will be helpful to better explain the pharmacological modulation of this pivotal membrane receptor by PPARγ agonists.

Molecular motors and nuclear movements in muscle

Muscle fibers have the particularity of containing numerous nuclei evenly distributed and positioned next to the plasma membrane. This unique disposition is the result of sequential events of nuclear movements that start when myoblasts fuse together and end with the clustering of few nuclei under the neuromuscular junction. Nuclei are mispositioned in multiple muscle disorders therefore the mechanisms of nuclear positioning can be novel targets for muscle disorders therapies. The 2 first nuclear movements that occur upon myoblast fusion require different microtubule motors. We performed a siRNA screen against all the microtubules motors and quantified nuclei behavior after fusion and inside the myotube. The different motors we found to be involved in the nuclear behaviors and the analysis of motors expression suggest a competition between both movement mechanisms, which potentially relies on the discrepancy between myoblast and myotube microtubules stability.

Targeted Nanotechnology in Glioblastoma Multiforme

Gliomas, and in particular glioblastoma multiforme, are aggressive brain tumors characterized by a poor prognosis and high rates of recurrence. Current treatment strategies are based on open surgery, chemotherapy (temozolomide) and radiotherapy. However, none of these treatments, alone or in combination, are considered effective in managing this devastating disease, resulting in a median survival time of less than 15 months. The efficiency of chemotherapy is mainly compromised by the blood-brain barrier (BBB) that selectively inhibits drugs from infiltrating into the tumor mass. Cancer stem cells (CSCs), with their unique biology and their resistance to both radio- and chemotherapy, compound tumor aggressiveness and increase the chances of treatment failure. Therefore, more effective targeted therapeutic regimens are urgently required. In this article, some well-recognized biological features and biomarkers of this specific subgroup of tumor cells are profiled and new strategies and technologies in nanomedicine that explicitly target CSCs, after circumventing the BBB, are detailed. Major achievements in the development of nanotherapies, such as organic poly(propylene glycol) and poly(ethylene glycol) or inorganic (iron and gold) nanoparticles that can be conjugated to metal ions, liposomes, dendrimers and polymeric micelles, form the main scope of this summary. Moreover, novel biological strategies focused on manipulating gene expression (small interfering RNA and clustered regularly interspaced short palindromic repeats [CRISPR]/CRISPR associated protein 9 [Cas 9] technologies) for cancer therapy are also analyzed. The aim of this review is to analyze the gap between CSC biology and the development of targeted therapies. A better understanding of CSC properties could result in the development of precise nanotherapies to fulfill unmet clinical needs.

KIF13B establishes a CAV1-enriched microdomain at the ciliary transition zone to promote Sonic hedgehog signalling

Ciliary membrane composition is controlled by transition zone (TZ) proteins such as RPGRIP1, RPGRIPL and NPHP4, which are vital for balanced coordination of diverse signalling systems like the Sonic hedgehog (Shh) pathway. Activation of this pathway involves Shh-induced ciliary accumulation of Smoothened (SMO), which is disrupted by disease-causing mutations in TZ components. Here we identify kinesin-3 motor protein KIF13B as a novel member of the RPGRIP1N-C2 domain-containing protein family and show that KIF13B regulates TZ membrane composition and ciliary SMO accumulation. KIF13B is upregulated during ciliogenesis and is recruited to the ciliary base by NPHP4, which binds to two distinct sites in the KIF13B tail region, including an RPGRIP1N-C2 domain. KIF13B and NPHP4 are both essential for establishment of a CAV1 membrane microdomain at the TZ, which in turn is required for Shh-induced ciliary SMO accumulation. Thus KIF13B is a novel regulator of ciliary TZ configuration, membrane composition and Shh signalling.

Antiangiogenic Therapeutic Potential of Peptides Derived from the Molecular Motor KIF13B that Transports VEGFR2 to Plasmalemma in Endothelial Cells

Vascular endothelial growth factor receptor 2 (VEGFR2) localized on the surface of endothelial cells (ECs) is a key determinant of the magnitude and duration of angiogenesis induced by vascular endothelial growth factor (VEGF). The kinesin family plus-end motor KIF13B transports VEGFR2 to the EC surface, and as such, specific inhibition of polarized VEGFR2 trafficking prevents angiogenesis. We designed a series of bioactive peptides based on deep analysis of VEGFR2-binding domain of KIF13B that compete specifically with VEGFR2 binding of KIF13B and thereby potently inhibit angiogenesis. Expression of these peptides by lentivirus prevents VEGF-induced capillary network formation in Matrigel plugs and neovascularization in vivo. A synthetic soluble, cell-permeable, 23-amino acid peptide termed kinesin-derived angiogenesis inhibitor (KAI) not only prevents interaction of VEGFR2 with KIF13B but also trafficking of VEGFR2 in the plus-end direction to the EC plasmalemma. Kinesin-derived angiogenesis inhibitor also inhibits VEGF-induced EC migration and tumor growth in human lung carcinoma xenografted in immunodeficient mice. Thus, we describe a novel class of peptides derived from the site of interaction of KIF13B with VEGFR2 that inhibit VEGFR2 trafficking and thereby starve cancer of blood supply.

An Atypical MAGUK GK Target Recognition Mode Revealed by the Interaction between DLG and KIF13B

The membrane-associated guanylate kinase (MAGUK) scaffold proteins share a signature guanylate kinase (GK) domain. Despite their diverse functional roles in cell polarity control and synaptic signaling, the currently known mode of action of MAGUK GK is via its binding to phosphorylated short peptides from target proteins. Here, we discover that the GK domain of DLG MAGUK binds to an unphosphorylated and autonomously folded domain within the stalk region (MAGUK binding stalk [MBS] domain) of a kinesin motor KIF13B with high specificity and affinity. The structure of DLG4 GK in complex with KIF13B MBS reveals the molecular mechanism governing this atypical GK/target recognition mode and provides insights into DLG/KIF13B complex-mediated regulation of diverse cellular processes such as asymmetric cell division. We further show that binding to non-phosphorylated targets is another general property of MAGUK GKs, thus expanding the mechanisms of action of the MAGUK family proteins.

Kif13b Regulates PNS and CNS Myelination through the Dlg1 Scaffold

Microtubule-based kinesin motors have many cellular functions, including the transport of a variety of cargos. However, unconventional roles have recently emerged, and kinesins have also been reported to act as scaffolding proteins and signaling molecules. In this work, we further extend the notion of unconventional functions for kinesin motor proteins, and we propose that Kif13b kinesin acts as a signaling molecule regulating peripheral nervous system (PNS) and central nervous system (CNS) myelination. In this process, positive and negative signals must be tightly coordinated in time and space to orchestrate myelin biogenesis. Here, we report that in Schwann cells Kif13b positively regulates myelination by promoting p38γ mitogen-activated protein kinase (MAPK)-mediated phosphorylation and ubiquitination of Discs large 1 (Dlg1), a known brake on myelination, which downregulates the phosphatidylinositol 3-kinase (PI3K)/v-AKT murine thymoma viral oncogene homolog (AKT) pathway. Interestingly, Kif13b also negatively regulates Dlg1 stability in oligodendrocytes, in which Dlg1, in contrast to Schwann cells, enhances AKT activation and promotes myelination. Thus, our data indicate that Kif13b is a negative regulator of CNS myelination. In summary, we propose a novel function for the Kif13b kinesin in glial cells as a key component of the PI3K/AKT signaling pathway, which controls myelination in both PNS and CNS.

Kif13b is an unconventional kinesin that acts as a signaling molecule, regulating myelination via the Dlg1 scaffold in both Schwann cells (in the peripheral nervous system) and oligodendrocytes (in the central nervous system).

Myelin is a multilayered extension of the Schwann and oligodendrocyte cell membranes, which wraps around neuronal axons to facilitate propagation of electric signals and to support axonal metabolism. However, the signals regulating myelin formation and how they are integrated and controlled to achieve homeostasis are still poorly understood.

In Schwann cells, the Discs large 1 (Dlg1) protein is a known brake of myelination, which negatively regulates the amount of myelin produced so that myelin thickness is proportional to axonal diameter. In this paper, we report that in Schwann cells Dlg1 itself is tightly regulated to ensure proper myelination. We propose that Dlg1 function is further controlled by the Kif13b kinesin motor protein, which acts as a "brake of the brake" by downregulating Dlg1 activity. Surprisingly, we found that in oligodendrocytes Dlg1 is a positive and not a negative regulator of myelination. Thus, Kif13b-mediated negative regulation of Dlg1 ensures appropriate myelin production and thickness in the central nervous system. Our data further extend recently emerged unconventional roles for kinesins, which are usually implicated in cargo transport rather than in the modulation of signaling pathways. The elucidation of mechanisms regulating myelination may help to design specific approaches to favor re-myelination in demyelinating disorders in which this process is severely impaired.

Genetics Underlying Atypical Parkinsonism and Related Neurodegenerative Disorders

Atypical parkinsonism syndromes, such as dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration, are neurodegenerative diseases with complex clinical and pathological features. Heterogeneity in clinical presentations, possible secondary determinants as well as mimic syndromes pose a major challenge to accurately diagnose patients suffering from these devastating conditions. Over the last two decades, significant advancements in genomic technologies have provided us with increasing insights into the molecular pathogenesis of atypical parkinsonism and their intriguing relationships to related neurodegenerative diseases, fueling new hopes to incorporate molecular knowledge into our diagnostic, prognostic and therapeutic approaches towards managing these conditions. In this review article, we summarize the current understanding of genetic mechanisms implicated in atypical parkinsonism syndromes. We further highlight mimic syndromes relevant to differential considerations and possible future directions.

Promising approaches to circumvent the blood-brain barrier: progress, pitfalls and clinical prospects in brain cancer

Brain drug delivery is a major challenge for therapy of central nervous system (CNS) diseases. Biochemical modifications of drugs or drug nanocarriers, methods of local delivery, and blood-brain barrier (BBB) disruption with focused ultrasound and microbubbles are promising approaches which enhance transport or bypass the BBB. These approaches are discussed in the context of brain cancer as an example in CNS drug development. Targeting to receptors enabling transport across the BBB offers noninvasive delivery of small molecule and biological cancer therapeutics. Local delivery methods enable high dose delivery while avoiding systemic exposure. BBB disruption with focused ultrasound and microbubbles offers local and noninvasive treatment. Clinical trials show the prospects of these technologies and point to challenges for the future.

Genome-wide association study of corticobasal degeneration identifies risk variants shared with progressive supranuclear palsy

Corticobasal degeneration (CBD) is a neurodegenerative disorder affecting movement and cognition, definitively diagnosed only at autopsy. Here, we conduct a genome-wide association study (GWAS) in CBD cases (n=152) and 3,311 controls, and 67 CBD cases and 439 controls in a replication stage. Associations with meta-analysis were 17q21 at MAPT (P=1.42 × 10(-12)), 8p12 at lnc-KIF13B-1, a long non-coding RNA (rs643472; P=3.41 × 10(-8)), and 2p22 at SOS1 (rs963731; P=1.76 × 10(-7)). Testing for association of CBD with top progressive supranuclear palsy (PSP) GWAS single-nucleotide polymorphisms (SNPs) identified associations at MOBP (3p22; rs1768208; P=2.07 × 10(-7)) and MAPT H1c (17q21; rs242557; P=7.91 × 10(-6)). We previously reported SNP/transcript level associations with rs8070723/MAPT, rs242557/MAPT, and rs1768208/MOBP and herein identified association with rs963731/SOS1. We identify new CBD susceptibility loci and show that CBD and PSP share a genetic risk factor other than MAPT at 3p22 MOBP (myelin-associated oligodendrocyte basic protein).

Kinesin superfamily proteins (KIFs): Various functions and their relevance for important phenomena in life and diseases

Kinesin superfamily proteins (KIFs) largely serve as molecular motors on the microtubule system and transport various cellular proteins, macromolecules, and organelles. These transports are fundamental to cellular logistics, and at times, they directly modulate signal transduction by altering the semantics of informational molecules. In this review, we will summarize recent approaches to the regulation of the transport destinations and to the physiological relevance of the role of these proteins in neuroscience, ciliary functions, and metabolic diseases. Understanding these burning questions will be essential in establishing a new paradigm of cellular functions and disease pathogenesis.

A novel assay reveals preferential binding between Rabs, kinesins, and specific endosomal subpopulations

A novel assay based on expressing FRB-tagged candidate vesicle-binding protein reveals that KIF13A and KIF13B bind preferentially to early endosomes, whereas KIF1A and KIF1Bβ bind preferentially to late endosomes and lysosomes.

Identifying the proteins that regulate vesicle trafficking is a fundamental problem in cell biology. In this paper, we introduce a new assay that involves the expression of an FKBP12-rapamycin–binding domain–tagged candidate vesicle-binding protein, which can be inducibly linked to dynein or kinesin. Vesicles can be labeled by any convenient method. If the candidate protein binds the labeled vesicles, addition of the linker drug results in a predictable, highly distinctive change in vesicle localization. This assay generates robust and easily interpretable results that provide direct experimental evidence of binding between a candidate protein and the vesicle population of interest. We used this approach to compare the binding of Kinesin-3 family members with different endosomal populations. We found that KIF13A and KIF13B bind preferentially to early endosomes and that KIF1A and KIF1Bβ bind preferentially to late endosomes and lysosomes. This assay may have broad utility for identifying the trafficking proteins that bind to different vesicle populations.