ABSTRACT
Enzymes or enzyme complexes can be concentrated in different cellular loci to modulate distinct functional processes in response to specific signals. How cells condense and compartmentalize enzyme complexes for spatiotemporally distinct cellular events is not well understood. Here we discover that specific and tight association of GIT1 and ß-Pix, a pair of GTPase regulatory enzymes, leads to phase separation of the complex without additional scaffolding molecules. GIT1/ß-Pix condensates are modular in nature and can be positioned at distinct cellular compartments, such as neuronal synapses, focal adhesions, and cell-cell junctions, by upstream adaptors. Guided by the structure of the GIT/PIX complex, we specifically probed the role of phase separation of the enzyme complex in cell migration and synapse formation. Our study suggests that formation of modular enzyme complex condensates via phase separation can dynamically concentrate limited quantities of enzymes to distinct cellular compartments for specific and optimal signaling.
Subject(s)
Cell Cycle Proteins/metabolism , GTPase-Activating Proteins/metabolism , Rho Guanine Nucleotide Exchange Factors/metabolism , Signal Transduction , Animals , Cell Cycle Proteins/chemistry , GTPase-Activating Proteins/chemistry , HEK293 Cells , HeLa Cells , Humans , Mice , Models, Molecular , Paxillin/metabolism , Protein Binding , Recombinant Proteins/metabolismABSTRACT
Primitive erythropoiesis serves a vital role in embryonic development, generating primitive red blood cells responsible for transportation of oxygen throughout the body. Although diverse niche factors are known to function in definitive hematopoiesis, the microenvironment contributing to primitive hematopoiesis remains largely elusive. Here, we report that platelet-derived growth factor (PDGF) signaling is required for erythroid progenitor differentiation in zebrafish. Ablating pdgfαa (also known as pdgfaa) and pdgfαb (also known as pdgfab) or blocking PDGF signaling with an inhibitor impairs erythroid progenitor differentiation, thus resulting in a significant decrease in the number of erythrocytes. We reveal that pdgfαb is expressed in sclerotomal cells, and that its receptor genes, pdgfra and pdgfrb, are expressed in the adjacent erythroid progenitor cells. Sclerotome-specific overexpression of pdgfαb effectively restores primitive erythropoiesis in pdgfαa-/-;pdgfαb-/- mutant embryos. In addition, we have defined ERK1/2 signaling as a downstream pathway of PDGF signaling during embryonic erythropoiesis. Taken together, our findings indicate that PDGF signaling derived from sclerotome functions as a niche cue for primitive erythropoiesis.
Subject(s)
Erythropoiesis , Platelet-Derived Growth Factor , Animals , Erythropoiesis/genetics , Zebrafish , Cues , Cell Differentiation/genetics , Embryonic DevelopmentABSTRACT
OBJECTIVE: This study aims to use the texture analysis of ultrasound images to distinguish the features of microchambers (a superficial thinner layer) and macrochambers (a deep thicker layer) in heel pads between the elderly with and without diabetes, so as to preliminarily explore whether texture analysis can identify the potential injury characteristics of deep tissue under the influence of diabetes before the obvious injury signs can be detected in clinical management. METHODS: Ultrasound images were obtained from the right heel (dominant leg) of eleven elderly people with diabetes (DM group) and eleven elderly people without diabetes (Non-DM group). The TekScan system was used to measure the peak plantar pressure (PPP) of each participant. Six gray-level co-occurrence matrix (GLCM) features including contrast, correlation, dissimilarity, energy, entropy, homogeneity were used to quantify texture changes in microchambers and macrochambers of heel pads. RESULTS: Significant differences in GLCM features (correlation, energy and entropy) of macrochambers were found between the two groups, while no significant differences in all GLCM features of microchambers were found between the two groups. No significant differences in PPP and tissue thickness in the heel region were observed between the two groups. CONCLUSIONS: In the elderly with diabetes who showed no significant differences in PPP and plantar tissue thickness compared to those without diabetes, several texture features of ultrasound images were found to be significantly different. Our finding indicates that texture features (correlation, energy and entropy) of macrochambers could be used for early detection of soft tissue damage associated with diabetes.
ABSTRACT
The axon initial segment (AIS) has characteristically dense clustering of voltage-gated sodium channels (Nav), cell adhesion molecule Neurofascin 186 (Nfasc), and neuronal scaffold protein Ankyrin-G (AnkG) in neurons, which facilitates generation of an action potential and maintenance of axonal polarity. However, the mechanisms underlying AIS assembly, maintenance, and plasticity remain poorly understood. Here, we report the high-resolution crystal structure of the AnkG ankyrin repeat (ANK repeat) domain in complex with its binding site in the Nfasc cytoplasmic tail that shows, in conjunction with binding affinity assays with serial truncation variants, the molecular basis of AnkG-Nfasc binding. We confirm AnkG interacts with the FIGQY motif in Nfasc, and we identify another region required for their high affinity binding. Our structural analysis revealed that ANK repeats form 4 hydrophobic or hydrophilic layers in the AnkG inner groove that coordinate interactions with essential Nfasc residues, including F1202, E1204, and Y1212. Moreover, we show disruption of the AnkG-Nfasc complex abolishes Nfasc enrichment at the AIS in cultured mouse hippocampal neurons. Finally, our structural and biochemical analysis indicated that L1 syndrome-associated mutations in L1CAM, a member of the L1 immunoglobulin family proteins including Nfasc, L1CAM, NrCAM, and CHL1, compromise binding with ankyrins. Taken together, these results define the mechanisms underlying AnkG-Nfasc complex formation and show that AnkG-dependent clustering of Nfasc is required for AIS integrity.
Subject(s)
Ankyrin Repeat , Ankyrins , Axon Initial Segment , Cell Adhesion Molecules , Nerve Growth Factors , Animals , Ankyrins/chemistry , Axon Initial Segment/chemistry , Binding Sites , Cell Adhesion Molecules/chemistry , Cell Adhesion Molecules/genetics , Crystallography, X-Ray , Mice , Nerve Growth Factors/chemistry , Nerve Growth Factors/genetics , Neural Cell Adhesion Molecule L1/genetics , Neural Cell Adhesion Molecule L1/metabolism , Protein DomainsABSTRACT
Harmonin is a protein containing multiple PDZ domains and is required for the development and maintenance of hair cell stereocilia and brush border microvilli. Mutations in the USH1C gene can cause Usher syndrome type 1C, a severe inheritable disease characterized by the loss of hearing and vision. Here, by solving the high-resolution crystal structure of Harmonin PDZ2 and coiled-coil domains in a complex with the tail of cadherin-related family member 2, we demonstrated that mutations located in the Harmonin PDZ2 domain and found in patients could affect its stability, and thus, the target binding capability. The structure also implies that the coiled-coil domain could form antiparallel dimers under high concentrations, possibly when Harmonin underwent liquid-liquid phase separation in the upper tip-link density in hair cell stereocilia or microvilli of enterocytes of the intestinal epithelium. The crystal structure, together with the biochemical analysis, provided mechanistic implications for Harmonin mutations causing Usher syndrome, non-syndromic deafness, or enteropathy.
Subject(s)
Usher Syndromes , Cadherins/genetics , Cadherins/metabolism , Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , Cytoskeletal Proteins/genetics , Cytoskeletal Proteins/metabolism , Humans , Protein Binding , Usher Syndromes/geneticsABSTRACT
Ankyrin-G (AnkG), a highly enriched scaffold protein in the axon initial segment (AIS) of neurons, functions to maintain axonal polarity and the integrity of the AIS. At the AIS, AnkG regulates selective intracellular cargo trafficking between soma and axons via interaction with the dynein regulator protein Ndel1, but the molecular mechanism underlying this binding remains elusive. Here we report that Ndel1's C-terminal coiled-coil region (CT-CC) binds to giant neuron-specific insertion regions present in both AnkG and AnkB with 2:1 stoichiometry. The high-resolution crystal structure of AnkB in complex with Ndel1 CT-CC revealed the detailed molecular basis governing the AnkB/Ndel1 complex formation. Mechanistically, AnkB binds with Ndel1 by forming a stable 5-helix bundle dominated by hydrophobic interactions spread across 6 distinct interaction layers. Moreover, we found that AnkG is essential for Ndel1 accumulation at the AIS. Finally, we found that cargo sorting at the AIS can be disrupted by blocking the AnkG/Ndel1 complex formation using a peptide designed based on our structural data. Collectively, the atomic structure of the AnkB/Ndel1 complex together with studies of cargo sorting through the AIS establish the mechanistic basis for AnkG/Ndel1 complex formation and for the maintenance of axonal polarity. Our study will also be valuable for future studies of the interaction between AnkB and Ndel1 perhaps at distal axonal cargo transport.
Subject(s)
Ankyrins/metabolism , Carrier Proteins/metabolism , Cell Polarity/physiology , Dyneins/metabolism , Neurons/metabolism , Ankyrins/chemistry , Axon Initial Segment , Axons/metabolism , Carrier Proteins/chemistry , Dyneins/chemistry , Microtubule-Associated Proteins , Models, Molecular , Protein Binding , Protein Conformation , Protein Interaction Domains and Motifs , Protein TransportABSTRACT
OBJECTIVE: Peak blood lactate at 24 h after extracorporeal membrane oxygenation (ECMO) can predict 30-day mortality in infants after complex cardiac surgery. METHODS: Twenty-eight infants with ECMO after complex congenital heart disease surgery were selected from March 2019 to March 2022 in our hospital. The infants were divided into survival group (n = 11) and non-survival group (n = 17) according to 30-day survival after discharge from hospital. The risk factors at 30-day mortality after discharge were analyzed by Cox regression analysis. RESULTS: When compared to the non-survival group, there were significant differences in peak blood lactate at 24 h after ECMO, liver dysfunction and multiple organ dysfunction syndrome (MODS) in the survival group (p < 0.05). Cox regression analysis showed that peak blood lactate at 24 h after ECMO (HR = 1.074, 95% CI: 1.005-1.149, p = 0.036) and MODS (HR = 4.120, 95% CI: 1.373-12.362, p = 0.012) were related risk factors affecting the prognosis of infants. The best cutoff value for the peak blood lactate at 24 h after ECMO was 10.2 mmol/L. The area under the curve (AUC) for predicting the 30-day survival rate of the ECMO assisted infants after discharge from hospital was 0.770 (95% CI: 0.592-0.948, p = 0.018), with a sensitivity of 94.1% and specificity of 54.5%. CONCLUSION: The peak blood lactate at 24 h after ECMO can predict the 30-day mortality after discharge of infants treated with ECMO after complex cardiac surgery. The best cut-off value for peak blood lactate at 24 h after ECMO was 10.2 mmol/L.
Subject(s)
Cardiac Surgical Procedures , Extracorporeal Membrane Oxygenation , Infant , Humans , Retrospective Studies , Cardiac Surgical Procedures/adverse effects , Prognosis , LactatesABSTRACT
To improve the aqueous solubility and oral bioavailability of paclitaxel (PTX), a biomimetic system for oral administration of PTX was efficiently developed as an outer membrane vesicle (OMVs) of sodium caseinate (CAS) modified zein nanoparticles (OMVs-Zein-CAS-PTX-NPs) by Escherichia coli. To verify their structure and properties, the designed nanostructures were thoroughly characterized using various characterization techniques. The results indicated that hydrogen bonds and van der Waals forces mainly drove the interaction between PTX and Zein, but the complex is unstable. The physicochemical stability of PTX-loaded zein nanoparticles was improved by the addition of CAS. The biological characteristics of biofilms are reproduced by nanoparticles cloaked with outer membrane vesicles. OMVs-Zein-CAS-PTX-NPs delayed the release of PTX under simulated gastric and intestinal fluids due to OMVs protection. OMVs-Zein-CAS-PTX-NPs exhibited remarkable antitumor ability in vitro and improved the bioavailability of oral administration of PTX in vivo. Therefore, OMVs cloaked in nanoparticles may be a suitable delivery vehicle to provide an efficient application prospect for the oral administration of PTX.
Subject(s)
Nanoparticles , Zein , Paclitaxel , Zein/chemistry , Drug Carriers/chemistry , Bacterial Outer Membrane , Nanoparticles/chemistryABSTRACT
This study investigated the clinical role of HOTAIR in patients with carotid artery stenosis (CAS) and its mechanism in vascular smooth muscle cells (VSMCs). Patients with CAS were collected. The expression of HOTAIR was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The clinical importance of HOTAIR was revealed by the receiver operating characteristic curve. Overexpression and knockdown of HOTAIR were achieved by transfecting pCDNA3.1-HOTAIR plasmid and si-HOTAIR respectively. CCK-8 assay or Transwell assay were used to analyze the changes in cell viability or migration after transfection treatments. Double luciferase reporter gene assay confirmed the targeted relationship between HOTAIR and miR-148b-3p. The levels of miR-148b-3p in VSMCs and patients were detected by qRT-PCR. Pearson analysis was used to analyze the relationship between HOTAIR and miR-148b-3p in patients with CAS. The expression of HOTAIR in patients with CAS was significantly higher than that in healthy individuals. HOTAIR appeared to discriminate CAS patients from healthy people. The overexpression of HOTAIR increased the viability and migration of VSMCs. Silenced HOTAIR restricted the abnormal viability and migration of VSMCs. A double luciferase reporter revealed a region of complementary binding between HOTAIR and miR-148b-3p. The expression of miR-148b-3p in VSMCs was regulated by the levels of HOTAIR. Reduction of miR-148b-3p expression was substantiated in CAS patients. Pearson analysis exhibited that the expression of HOTAIR was negatively relative to the levels of miR-148b-3p. The long noncoding RNA HOTAIR might be a diagnostic biomarker for CAS patients, and it was involved in the activity of vascular smooth muscle cells.
Subject(s)
Carotid Stenosis , MicroRNAs , RNA, Long Noncoding , Humans , RNA, Long Noncoding/genetics , Muscle, Smooth, Vascular/metabolism , MicroRNAs/genetics , MicroRNAs/metabolism , Cell Proliferation/genetics , Carotid Stenosis/genetics , Carotid Stenosis/metabolism , Myocytes, Smooth Muscle/metabolism , Cell Movement/geneticsABSTRACT
Intermittent pneumatic compression (IPC) is commonly used to improve peripheral circulation of the lower extremity. However, its therapeutic dosage for people with type 2 diabetes mellitus (DM) at risk for ulcers is not well established. This study explored the effect of IPC with different inflation pressures on the distal microvascular responses of the foot in people with type 2 DM. Twenty-four subjects with and without DM were recruited. Three IPC protocols with inflation pressures of 60, 90, and 120 mmHg were applied to the foot. The foot skin blood flow (SBF) responses were measured by laser Doppler flowmetry during and after IPC interventions. Results show that all three IPC interventions significantly increased foot SBF of IPC stage in healthy subjects, but only 90 and 120 mmHg IPC significantly improved SBF in diabetic subjects. IPC with 90 and 120 mmHg showed a greater effect than 60 mmHg in both groups, but 120 mmHg IPC was more effective for diabetic subjects. This study demonstrates that 90 and 120 mmHg are effective dosages of IPC for improving blood flow in healthy people, and 120 mmHg IPC may be more suitable for people with type 2 DM.
Subject(s)
Diabetes Mellitus, Type 2 , Leg , Blood Flow Velocity/physiology , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/therapy , Humans , Intermittent Claudication/therapy , Intermittent Pneumatic Compression Devices , Leg/blood supplyABSTRACT
Natural systems can undergo critical transitions, leading to substantial socioeconomic and ecological outcomes. "Ecological resilience" has been proposed to describe the capacity of natural systems to absorb external perturbation and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedbacks. However, the mere application of ecological resilience in theoretical research and the lack of quantitative approaches present considerable obstacles for predicting critical transitions and understanding their mechanisms. Large marine ecosystems (LMEs) in the Northwestern Pacific are characterized by great biodiversity and productivity, as well as remarkable warming in recent decades. However, no information is available on the critical transitions and ecological resilience of LMEs in response to warming. Therefore, we applied an integrated resilience assessment framework to fisheries catch data from seven LMEs covering a wide range of regions, from tropical to subarctic, in the Northwestern Pacific to identify critical transitions, assess ecological resilience, and reconstruct folded stability landscapes, with a specific focus on the effects of warming. The results provide evidence of the occurrence of critical transitions, with fold bifurcation and hysteresis in response to increasing sea surface temperatures (SSTs) in the seven LMEs. In addition, these LMEs show similarities and synchronies in structure variations and critical transitions forced by warming. Both dramatic increases in SST and small fluctuations at the corresponding thresholds may trigger critical transitions. Ecological resilience decreases when approaching the tipping points and is repainted as the LMEs shift to alternative stable states with different resilient dynamics. Folded stability landscapes indicate that the responses of LMEs to warming are discontinuous, which may be caused by the reorganization of LMEs as their sensitivity to warming changes. Our study clarifies the nonlinear responses of LMEs to anthropogenic warming and provides examples of quantifying ecological resilience in empirical systems at unprecedented spatial and temporal scales.
Subject(s)
Ecosystem , Global Warming , Biodiversity , Fisheries , TemperatureABSTRACT
AIM: Atherosclerosis (AS) is one of the main causes of cardiovascular disease which might lead to myocardial infarction or stroke and further leads to fatality. METHOD: In this study, we have designed an anti-inflammatory cytokine interleukin-10 (IL10) delivery system to effectively alleviate the inflammation of atherosclerosis plaque. The targeted delivery of IL10 to the atherosclerotic plaques was achieved by cRGD conjugated liposomes (IL10-cRGD-Lip). RESULTS: The IL10-cRGD-Lip of size 179.4 ± 10.91 nm having PDI 0.14 ± 0.04 with a surface charge of +18.34 ± 1.36 mV was prepared. The in-vitro analysis clearly suggests that IL10-cRGD-Lip sustains the release of IL10 and could significantly reduce ROS and NO. The immuno-staining results revealed that IL-1ß and TNF-α were down-regulated after the treatment with IL10-cRGD-Lip in Lipopolysaccharide (LPS) stimulated RAW 264.7 cells. CONCLUSION: the in-vitro results clearly suggest that anti-inflammatory cytokine IL10 could be used for the cure of inflammatory maladies including atherosclerosis.
Subject(s)
Atherosclerosis , Liposomes , Anti-Inflammatory Agents , Atherosclerosis/drug therapy , Cytokines , Humans , Interleukin-10ABSTRACT
Lysine methylation of cellular proteins is catalyzed by dozens of lysine methyltransferases (KMTs), occurs in thousands of different histone and nonhistone proteins, and regulates diverse biological processes. Dysregulation of KMT-mediated lysine methylations underlies many human diseases. A key unanswered question is how proteins, nonhistone proteins in particular, are specifically methylated by each KMT. Here, using several biochemical approaches, including analytical gel filtration chromatography, isothermal titration calorimetry, and in vitro methylation assays, we discovered that SET domain-containing 7 histone lysine methyltransferase (SETD7), a KMT capable of methylating both histone and nonhistone proteins, uses its N-terminal membrane occupation and recognition nexus (MORN) repeats to dock its substrates and subsequently juxtapose their Lys methylation motif for efficient and specific methylation by the catalytic SET domain. Such docking site-mediated methylation mechanism rationalizes binding and methylation of previously known substrates and predicts new SETD7 substrates. Our findings further suggest that other KMTs may also use docking-mediated substrate recognition mechanisms to achieve their catalytic specificity and efficiency.
Subject(s)
Histone-Lysine N-Methyltransferase/metabolism , Lysine/metabolism , Biocatalysis , Catalytic Domain , Humans , Methylation , Substrate SpecificityABSTRACT
The mammalian Atg8 family proteins are central drivers of autophagy and contain six members, classified into the LC3 and GABARAP subfamilies. Due to their high sequence similarity and consequent functional overlaps, it is difficult to delineate specific functions of Atg8 proteins in autophagy. Here we discover a super-strong GABARAP-selective inhibitory peptide harbored in 270/480 kDa ankyrin-G and a super-potent pan-Atg8 inhibitory peptide from 440 kDa ankyrin-B. Structural studies elucidate the mechanism governing the Atg8 binding potency and selectivity of the peptides, reveal a general Atg8-binding sequence motif, and allow development of a more GABARAP-selective inhibitory peptide. These peptides effectively blocked autophagy when expressed in cultured cells. Expression of these ankyrin-derived peptides in Caenorhabditis elegans also inhibited autophagy, causing accumulation of the p62 homolog SQST-1, delayed development and shortened life span. Thus, these genetically encodable autophagy inhibitory peptides can be used to occlude autophagy spatiotemporally in living animals.
Subject(s)
Ankyrins/chemistry , Autophagy-Related Protein 8 Family/antagonists & inhibitors , Autophagy/drug effects , Peptides/pharmacology , Animals , Autophagy-Related Protein 8 Family/metabolism , COS Cells , Cells, Cultured , Chlorocebus aethiops , Peptides/chemistryABSTRACT
Unconventional myosins are a large superfamily of actin-based molecular motors that use ATP as fuel to generate mechanical motions/forces. The distinct tails in different unconventional myosin subfamilies can recognize various cargoes including proteins and lipids. Thus, they can play diverse roles in many biological processes such as cellular trafficking, mechanical supports, force sensing, etc. This chapter focuses on some recent advances on the structural studies of how unconventional myosins specifically bind to cargoes with their cargo-binding domains.
Subject(s)
Biological Transport , Myosins/metabolism , Actins , Protein BindingABSTRACT
Unconventional myosin 7a (Myo7a), myosin 7b (Myo7b), and myosin 15a (Myo15a) all contain MyTH4-FERM domains (myosin tail homology 4-band 4.1, ezrin, radixin, moesin; MF) in their cargo binding tails and are essential for the growth and function of microvilli and stereocilia. Numerous mutations have been identified in the MyTH4-FERM tandems of these myosins in patients suffering visual and hearing impairment. Although a number of MF domain binding partners have been identified, the molecular basis of interactions with the C-terminal MF domain (CMF) of these myosins remains poorly understood. Here we report the high-resolution crystal structure of Myo7b CMF in complex with the extended PDZ3 domain of USH1C (a.k.a., Harmonin), revealing a previously uncharacterized interaction mode both for MyTH4-FERM tandems and for PDZ domains. We predicted, based on the structure of the Myo7b CMF/USH1C PDZ3 complex, and verified that Myo7a CMF also binds to USH1C PDZ3 using a similar mode. The structure of the Myo7b CMF/USH1C PDZ complex provides mechanistic explanations for >20 deafness-causing mutations in Myo7a CMF. Taken together, these findings suggest that binding to PDZ domains, such as those from USH1C, PDZD7, and Whirlin, is a common property of CMFs of Myo7a, Myo7b, and Myo15a.
Subject(s)
Adaptor Proteins, Signal Transducing/chemistry , Multiprotein Complexes/chemistry , Myosins/chemistry , Adaptor Proteins, Signal Transducing/genetics , Adaptor Proteins, Signal Transducing/metabolism , Caco-2 Cells , Cell Cycle Proteins , Cytoskeletal Proteins , Humans , Multiprotein Complexes/genetics , Multiprotein Complexes/metabolism , Myosin VIIa , Myosins/genetics , Myosins/metabolism , PDZ Domains , Protein Structure, QuaternaryABSTRACT
Unconventional myosins are a superfamily of actin-based molecular motors playing diverse roles including cellular trafficking, mechanical supports, force sensing and transmission, etc. The variable neck and tail domains of unconventional myosins function to bind to specific cargoes including proteins and lipid vesicles and thus are largely responsible for the diverse cellular functions of myosins in vivo. In addition, the tail regions, together with their cognate cargoes, can regulate activities of the motor heads. This review outlines the advances made in recent years on cargo recognition and cargo binding-induced regulation of the activity of several unconventional myosins including myosin-I, V, VI and X in cellular trafficking. We approach this topic by describing a series of high-resolution structures of the neck and tail domains of these unconventional myosins either alone or in complex with their specific cargoes, and by discussing potential implications of these structural studies on cellular trafficking of these myosin motors.
Subject(s)
Actins/metabolism , Cell Movement/physiology , Models, Molecular , Myosins/metabolism , Protein Transport/physiology , Amino Acid Sequence/physiology , Animals , HumansABSTRACT
Organized motions are hallmarks of living organisms. Such motions range from collective cell movements during development and muscle contractions at the macroscopic scale all the way down to cellular cargo (e.g., various biomolecules and organelles) transportation and mechanoforce sensing at more microscopic scales. Energy required for these biological motions is almost invariably provided by cellular chemical fuels in the form of nucleotide triphosphate. Biological systems have designed a group of nanoscale engines, known as molecular motors, to convert cellular chemical fuels into mechanical energy. Molecular motors come in various forms including cytoskeleton motors (myosin, kinesin, and dynein), nucleic-acid-based motors, cellular membrane-based rotary motors, and so on. The main focus of this Account is one subfamily of actin filament-based motors called unconventional myosins (other than muscle myosin II, the remaining myosins are collectively referred to as unconventional myosins). In general, myosins can use ATP to fuel two types of mechanomotions: dynamic tethering actin filaments with various cellular compartments or structures and actin filament-based intracellular transport. In contrast to rich knowledge accumulated over many decades on ATP hydrolyzing motor heads and their interactions with actin filaments, how various myosins recognize their specific cargoes and whether and how cargoes can in return regulate functions of motors are less understood. Nonetheless, a series of biochemical and structural investigations in the past few years, including works from our own laboratory, begin to shed lights on these latter questions. Some myosins (e.g., myosin-VI) can function both as cellular transporters and as mechanical tethers. To function as a processive transporter, myosins need to form dimers or multimers. To be a mechanical tether, a monomeric myosin is sufficient. It has been shown for myosin-VI that its cellular cargo proteins can play critical roles in determining the motor properties. Dab2, an adaptor protein linking endocytic vesicles with actin-filament-bound myosin-VI, can induce the motor to form a transport competent dimer. Such a cargo-mediated dimerization mechanism has also been observed in other myosins including myosin-V and myosin-VIIa. The tail domains of myosins are very diverse both in their lengths and protein domain compositions and thus enable motors to engage a broad range of different cellular cargoes. Remarkably, the cargo binding tail of one myosin alone often can bind to multiple distinct target proteins. A series of atomic structures of myosin-V/cargo complexes solved recently reveals that the globular cargo binding tail of the motor contains a number of nonoverlapping target recognition sites for binding to its cargoes including melanophilin, vesicle adaptors RILPL2, and vesicle-bound GTPase Rab11. The structures of the MyTH4-FERM tandems from myosin-VIIa and myosin-X in complex with their respective targets reveal that MyTH4 and FERM domains extensively interact with each other forming structural and functional supramodules in both motors and demonstrate that the structurally similar MyTH4-FERM tandems of the two motors display totally different target binding modes. These structural studies have also shed light on why numerous mutations found in these myosins can cause devastating human diseases such as deafness and blindness, intellectual disabilities, immune disorders, and diabetes.
Subject(s)
Myosins/metabolism , Models, Molecular , Myosins/chemistryABSTRACT
OBJECTIVE: To analyze the value of 2- and 9-question patient health questionnaires (PHQ-2 and PHQ-9) for screening status of depression in cardiovascular outpatients. METHODS: From June 2013 to January 2014, a total of 201 outpatients from psycho-cardiological outpatients departments were consecutively enrolled into this study. All patients were asked to complete PHQ-9 and the mental psychological assessment by qualified researchers trained by psychiatry according to the composite international diagnostic interviews (CIDI), 50 cases were retested to assess the retest reliability after one week. The PHQ-2 and PHQ-9 were validated with the CIDI as the reference criteria. RESULTS: According to the CIDI, 42 (21.3%) out of the 201 outpatients were diagnosed as depression. For PHQ-9 scale, a cutoff value of 10 presented satisfactory results with 87.1% sensitivity, 83.5% specificity, 58.7% positive predicting value, 95.6% negative predicting value and the area under the ROC curve (AUC) was 0.877 (SE = 0.032, 95% CI: 0.813-0.938). The Cronbach's alpha coefficients and test-retest reliability of the PHQ-9 were 0.809 and 0.882, respectively. Compared with CIDI, the cutoff value of the PHQ-2 was 3 with 85.7% sensitivity, 69.2% specificity, 57.1% positive predicting value, 93.6% negative predicting value, and the AUC was 0.806 (SE = 0.042, 95% CI: 0.774-0.889). The Cronbach's alpha coefficients and test-retest reliability of the PHQ-2 were 0.785 and 0.813, respectively. CONCLUSION: The PHQ-2 and PHQ-9 are reliable and efficient instruments for screening and especially excluding depression in cardiovascular outpatients.
Subject(s)
Cardiovascular Diseases/psychology , Depression/diagnosis , Outpatients/psychology , Surveys and Questionnaires , Area Under Curve , Cardiovascular Diseases/complications , Humans , Mass Screening , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
OBJECTIVE: To explore if the new onset hypertension was related with metabolic risk factors and lifestyle in Beijing community residents to guide the targeted prevention of hypertension. METHODS: A population-based survey with a randomly cluster sampling was made to observe the relationship between metabolic risk factors and lifestyle with new onset hypertension by multivariate and logistic regression. RESULTS: A total of 4 034 subjects with normal blood pressure at baseline were included and 978 (24.2%) residents developed hypertension two years later. Multiple logistic analysis demonstrated that risk factors that contributed to new onset hypertension were prehypertension, overweight, obesity, frequent alcohol drinking, metabolic syndrome (MS), age and male gender, the respective Odds Ratios(OR) and 95% confidence interval (95%CI) are as follows: 3.512 (2.965-4.168), 1.654 (1.423-1.918), 2.264 (1.633-2.951), 1.493 (1.231-1.775), 1.329 (1.227-1.414), 1.226 (1.115-1.335), 1.135(1.018-1.221). College education serves as the protective factor, and the OR (95%CI) was 0.692 (0.476, 0.897). CONCLUSIONS: New onset hypertension in Beijing community residents is mainly related with prehypertension, overweight or obesity, MS, frequent alcohol drinking and low education level. We should pay more attention to modulating metabolic risk factors and lifestyle to reduce the new onset hypertension in China.