Myocardin reverses insulin resistance and ameliorates cardiomyopathy by increasing IRS-1 expression in a murine model of lipodystrophy caused by adipose deficiency of vacuolar H+-ATPase V0d1 subunit.

Aim: Adipose tissue (AT) dysfunction that occurs in both obesity and lipodystrophy is associated with the development of cardiomyopathy. However, it is unclear how dysfunctional AT induces cardiomyopathy due to limited animal models available. We have identified vacuolar H+-ATPase subunit Vod1, encoded by Atp6v0d1, as a master regulator of adipogenesis, and adipose-specific deletion of Atp6v0d1 (Atp6v0d1AKO) in mice caused generalized lipodystrophy and spontaneous cardiomyopathy. Using this unique animal model, we explore the mechanism(s) underlying lipodystrophy-related cardiomyopathy. Methods and Results: Atp6v0d1AKO mice developed cardiac hypertrophy at 12 weeks, and progressed to heart failure at 28 weeks. The Atp6v0d1AKO mouse hearts exhibited excessive lipid accumulation and altered lipid and glucose metabolism, which are typical for obesity- and diabetes-related cardiomyopathy. The Atp6v0d1AKO mice developed cardiac insulin resistance evidenced by decreased IRS-1/2 expression in hearts. Meanwhile, the expression of forkhead box O1 (FoxO1), a transcription factor which plays critical roles in regulating cardiac lipid and glucose metabolism, was increased. RNA-seq data and molecular biological assays demonstrated reduced expression of myocardin, a transcription coactivator, in Atp6v0d1AKO mouse hearts. RNA interference (RNAi), luciferase reporter and ChIP-qPCR assays revealed the critical role of myocardin in regulating IRS-1 transcription through the CArG-like element in IRS-1 promoter. Reducing IRS-1 expression with RNAi increased FoxO1 expression, while increasing IRS-1 expression reversed myocardin downregulation-induced FoxO1 upregulation in cardiomyocytes. In vivo, restoring myocardin expression specifically in Atp6v0d1AKO cardiomyocytes increased IRS-1, but decreased FoxO1 expression. As a result, the abnormal expressions of metabolic genes in Atp6v0d1AKO hearts were reversed, and cardiac dysfunctions were ameliorated. Myocardin expression was also reduced in high fat diet-induced diabetic cardiomyopathy and palmitic acid-treated cardiomyocytes. Moreover, increasing systemic insulin resistance with rosiglitazone restored cardiac myocardin expression and improved cardiac functions in Atp6v0d1AKO mice. Conclusion: Atp6v0d1AKO mice are a novel animal model for studying lipodystrophy- or metabolic dysfunction-related cardiomyopathy. Moreover, myocardin serves as a key regulator of cardiac insulin sensitivity and metabolic homeostasis, highlighting myocardin as a potential therapeutic target for treating lipodystrophy- and diabetes-related cardiomyopathy.

KV Channel-Interacting Proteins in the Neurological and Cardiovascular Systems: An Updated Review.

KV channel-interacting proteins (KChIP1-4) belong to a family of Ca2+-binding EF-hand proteins that are able to bind to the N-terminus of the KV4 channel α-subunits. KChIPs are predominantly expressed in the brain and heart, where they contribute to the maintenance of the excitability of neurons and cardiomyocytes by modulating the fast inactivating-KV4 currents. As the auxiliary subunit, KChIPs are critically involved in regulating the surface protein expression and gating properties of KV4 channels. Mechanistically, KChIP1, KChIP2, and KChIP3 promote the translocation of KV4 channels to the cell membrane, accelerate voltage-dependent activation, and slow the recovery rate of inactivation, which increases KV4 currents. By contrast, KChIP4 suppresses KV4 trafficking and eliminates the fast inactivation of KV4 currents. In the heart, IKs, ICa,L, and INa can also be regulated by KChIPs. ICa,L and INa are positively regulated by KChIP2, whereas IKs is negatively regulated by KChIP2. Interestingly, KChIP3 is also known as downstream regulatory element antagonist modulator (DREAM) because it can bind directly to the downstream regulatory element (DRE) on the promoters of target genes that are implicated in the regulation of pain, memory, endocrine, immune, and inflammatory reactions. In addition, all the KChIPs can act as transcription factors to repress the expression of genes involved in circadian regulation. Altered expression of KChIPs has been implicated in the pathogenesis of several neurological and cardiovascular diseases. For example, KChIP2 is decreased in failing hearts, while loss of KChIP2 leads to increased susceptibility to arrhythmias. KChIP3 is increased in Alzheimer's disease and amyotrophic lateral sclerosis, but decreased in epilepsy and Huntington's disease. In the present review, we summarize the progress of recent studies regarding the structural properties, physiological functions, and pathological roles of KChIPs in both health and disease. We also summarize the small-molecule compounds that regulate the function of KChIPs. This review will provide an overview and update of the regulatory mechanism of the KChIP family and the progress of targeted drug research as a reference for researchers in related fields.

Chronic blue light leads to accelerated aging in Drosophila by impairing energy metabolism and neurotransmitter levels.

Blue light (BL) is becoming increasingly prevalent in artificial illumination, raising concerns about its potential health hazard to humans. In fact, there is evidence suggesting that acute BL exposure may lead to oxidative stress and death of retinal cells specialized for photoreception. On the other hand, recent studies in Drosophila melanogaster demonstrated that chronic BL exposure across lifespan leads to accelerated aging manifested in reduced lifespan and brain neurodegeneration even in flies with genetically ablated eyes, suggesting that BL can damage cells and tissues not specialized for light perception. At the physiological level, BL exposure impairs mitochondria function in flies, but the metabolic underpinnings of these effects have not been studied. Here, we investigated effects of chronic BL on metabolic pathways in heads of eyes absent (eya 2 ) mutant flies in order to focus on extra-retinal tissues. We compared metabolomic profiles in flies kept for 10 or 14 days in constant BL or constant darkness, using LC-MS and GC-MS. Data analysis revealed significant alterations in the levels of several metabolites suggesting that critical cellular pathways are impacted in BL-exposed flies. In particular, dramatic metabolic rearrangements are observed in heads of flies kept in BL for 14 days, including highly elevated levels of succinate but reduced levels of pyruvate and citrate, suggesting impairments in energy production. These flies also show onset of neurodegeneration and our analysis detected significantly reduced levels of several neurotransmitters including glutamate and Gamma-aminobutyric acid (GABA), suggesting that BL disrupts brain homeostasis. Taken together, these data provide novel insights into the mechanisms by which BL interferes with vital metabolic pathways that are conserved between fly and human cells.

Age-dependent effects of blue light exposure on lifespan, neurodegeneration, and mitochondria physiology in Drosophila melanogaster.

Blue light is a predominant component of light emitting devices (LEDs), which are increasingly present in our environment. There is already accumulating evidence that blue light exposure causes damage to retinal cells in vitro and in vivo; however, much less is known about potential effects of blue light on non-retinal cells. That blue light may be detrimental at the organismal level independent from retinal effect was recently shown by findings that it reduces lifespan in worms and also in flies with genetically ablated retinas. Here, we investigated the effects of blue light exposure across the fly lifespan and found that susceptibility to blue light stress is strongly age-dependent. The blue light of the same intensity and duration reduced survival and increased neurodegeneration more significantly in old flies than in young flies. These differences appear to be caused, at least in part, by impairments of mitochondrial respiratory function. We report that blue light significantly reduces the activity of Complex II in the electron transport system and decrease the biochemical activity of succinate dehydrogenase in both young and old flies. In addition, complex I and complex IV activities are reduced by age, as are ATP levels. We therefore propose that older flies are more sensitive to blue light because the light-induced mitochondrial damage potentiates the age-related impairments in energy metabolism that occurs even in darkness. Taken together, our results show that damaging effects of blue light at the organismal level are strongly age dependent and are associated with reduced activity of specific components of energy producing pathways in mitochondria.

Measurement of solution properties and molecular weight of hydroxyethyl starches using multi-angle laser light scattering: An interlaboratory comparison.

The solution properties of hydroxyethyl starch (HES) vary significantly owing to different measurement parameters adopted and sample structures. Here, a round-robin study was conducted to compare inter-laboratory measurements of solution properties, weight-average molecular weight (Mw), and molecular weight distribution of four HES candidates covering the low- and medium-molecular-weight range, and 50 commercially available HES 130/0.4 drug samples. Analysis was performed using size exclusion chromatography (SEC) combined with multi-angle laser light scattering (MALLS) and differential refractive index (dRI) detectors. The results indicate that HES molecules in the Mw range of 17,000-130,000, with varying degrees of substitution (between 0.4 and 0.8), yielded a refractive index increment (dn/dc) value of 0.145 ± 0.003 mL/g (solvent: acetic acid-sodium acetate buffer; wavelength: 658 nm) and that the second virial coefficient (A2) is correlated with Mw. The SEC-MALLS-dRI method for Mw determination of HES demonstrated good inter-laboratory reproducibility; however, the study findings suggest that column specifications should be added for HES quality standards. Comparing Mw results obtained using common and experimentally corrected dn/dc and A2 values revealed an influence of dn/dc and A2 on Mw, indicating that the Mw acceptance criteria of HES quality standards should be adjusted.

Portable 3D Gait Analysis Assessment in MTT Treat Chronic Ankle Instability: A Retrospective Study.

PURPOSE: Retrospective analysis of the effect of portable 3D gait analysis as an innovative evaluation method in the treatment with MTT on chronic ankle instability patient. METHODS: From January 1, 2019, to December 31, 2019, 56 cases of chronic ankle instability (CAI) were extracted from the medical record system of Shenzhen Longhua District Central Hospital. All the patients of 56 cases accepted the medical training therapy (MTT). As outcome parameters, the alterations of the Cumberland ankle instability tool (CAIT), foot and ankle ability measure (FAAM), were used before the treatment and after treatment; meanwhile, the portable apparatus 3D gait analysis was used to measure the gait parameters. CONCLUSION: The results showed only ankle angle parameters Y-axis, maximum dorsiflexion during support period (°) had a significant difference, and the p value is 0.039. Meanwhile, the CAIT, FAAM, and most 3D gait analysis data had no significant difference. This particular statistical difference shows that CAI can be measured scientifically and objectively, although most measurement parameters have no change. These results make further reveal that the CAI patients are suffering with dynamic abnormality of ankle motion angle; this also provides us with a measurable and systematic evaluation reference plan for CAI treatment in the future.

Psychological Distress and Its Association With Quality of Life in Organ Transplant Recipients During COVID-19 Pandemic.

Objectives: The coronavirus disease 2019 (COVID-19) pandemic may have an impact on the psychological distress of organ transplant recipients. We aimed to assess the status of psychological distress and its association with quality of life (QoL) in organ transplant recipients during the COVID-19 pandemic. Materials and Methods: A cross-sectional survey was carried out with 305 organ transplant recipients during March 30 and April 2, 2020, in Wuhan. Psychological distress comprised depression, anxiety, insomnia, and post-traumatic stress disorder (PTSD), which were assessed using the Patient Health Questionnaire-9, the seven-item Generalized Anxiety Disorder questionnaire, the Insomnia Severity Index, and Impact of event scale-revised. QoL was assessed using the Chinese version of the short Form 36-item health survey. Results: The prevalence of depression, anxiety, insomnia, and PTSD in organ transplant recipients was 13.4, 6.9, 11.8, and 30.5%, respectively. Organ transplant recipients with depression had significantly lower scores in all eight dimensions of QoL compared with participants without depression (all p < 0.05). Lower scores on the QoL dimensions of role physical, bodily pain, general health, vitality, role emotional, and mental health were found in organ transplant recipients with anxiety, insomnia, or PTSD compared with their counterparts without the respective disorder (all p < 0.05). Limitation: The cross-sectional study design limited us to make causal conclusion and the influence of potential confounders cannot be ruled out. Conclusions: Psychological distress was prevalent in organ transplant recipients during the COVID-19 pandemic, and those with depression, anxiety, insomnia, and PTSD had poorer QoL. Therefore, timely psychological counseling, COVID-19 related health education, and essential community medical services should be provided to organ transplant recipients to relieve their psychological distress, and to improve their QoL.

[Efficacy and safety of body-insulated acupuncture needle for electrical stimulation at rabbit scia-tic nerve trunk].

OBJECTIVE: To evaluate the efficacy and safety of electrical stimulation at the rabbit sciatic nerve trunk with the body-insulated acupuncture needle whose body is painted with insulating material. METHODS: Eighteen male New Zealand rabbits were randomized into the body-insulated acupuncture needle (BIAN), the general acupuncture needle (GAN), and the blank control groups，with 6 rabbits in each group. The rats'sciatic nerve trunks in BIAN and GAN groups were stimulated by electroacupuncture with the body-insulated acupuncture needle (only allowing the uncoated needle handle and tip to conduct electricity) and the general acupuncture needle, separately. The current intensity was recorded when regular plantarflexion reflexes (sciatic nerve effector reflexes) were observed in the rabbit's foot. The pathological changes of the sciatic nerve at the acupuncture site were observed by H.E. staining, and the ultrastructural changes of the sciatic nerve trunk were observed by transmission electron microscope. RESULTS: The intensity of the current causing the regular plantar flexion reflection in BIAN group (ï¼»0.29±0.07ï¼½ mA) was significantly lower than that in the GAN group(ï¼»0.86±0.08ï¼½ mA, P<0.01). H.E. staining revealed nerve axon degeneration, forming eosinophilic bodies, nerve fiber edema, and focal loss of myelin sheath in the GAN group. While the nerve fiber damage was not obvious, and axons were only degenerated in a few areas in the BIAN group. Transmission electron microscopy observations showed that the nerve myelin sheath structure was separated, the layers were arranged disorderly and bubbled in the GAN group. while the nerve myelin sheath structure of the BIAN group was normal, and it presents a concentric circle-like light and dark lamellar structure, with fewer myelin vacuoles and fissures, only a small part of the mitochondria, microfilaments, and microtubules of the nerve axons were abnormal, and the overall vacuole-like degeneration was significantly reduced, with few of the myelinated fibers were slightly degenerated, and axonal disease was not obvious. CONCLUSION: Insulated acupuncture needle is more accurate and safer than ordinary acupuncture needle for electrical stimulation of rabbit sciatic nerve trunk, and the required electric current intensity is smaller.

Application of Wireless Dynamic Sleep Monitor in Acupuncture Treatment of Insomnia after Ischemic Stroke: A Retrospective Study.

PURPOSE: Retrospective analysis of the clinical effect of acupuncture on insomnia after ischemic stroke by using a wireless sleep monitor as an innovative evaluation method. METHODS: From March 1, 2018, to September 30, 2019, 105 cases of insomnia after ischemic stroke were extracted from the inpatient medical record system of Shenzhen Longhua District Central Hospital. According to differences in the treatment plan, the cases were divided into an acupuncture group (57 cases) and a drug group (48 cases). The acupuncture group was given acupuncture treatment on the basis of usual care, while the drug group was given estazolam oral treatment on the basis of usual care. Under the ICF framework, the related items of sleep function and emotion function were selected for evaluation. As outcome parameters, the alterations of the Pittsburgh sleep quality index (PSQI), the self-rating anxiety scale (SAS), and the self-rating depression scale (SDS) were used before the treatment, after treatment, and in a follow-up; meanwhile, the ActiSleep-BT wireless sleep monitor was used to measure total sleep time (TST), sleep efficiency (SE), and sleep arousal (SA) of the two groups before and after treatment and at follow-up. RESULTS: Within-group comparison showed significant differences in the acupuncture group before treatment and after treatment on the ActiSleep-BT wireless dynamic sleep monitor data as well as in PSQI and ICF. Comparing the acupuncture group with the control group also showed significant differences in the ActiSleep-BT wireless dynamic sleep monitor data, PSQI, and ICF. CONCLUSION: By evaluation using ActiSleep-BT wireless sleep monitor, acupuncture treated insomnia after ischemic stroke; the effect is better than usual care.

Transcriptomic and proteomic analysis of putative digestive proteases in the salivary gland and gut of Empoasca (Matsumurasca) onukii Matsuda.

BACKGROUND: Infestation by tea green leafhoppers (Empoasca (Matsumurasca) onukii) can cause a series of biochemical changes in tea leaves. As a typical cell-rupture feeder, E. onukii secretes proteases while using its stylet to probe the tender shoots of tea plants (Camellia sinensis). This study identified and analyzed proteases expressed specifically in the salivary gland (SG) and gut of E. onukii through enzymatic activity assays complemented with an integrated analysis of transcriptomic and proteomic data. RESULTS: In total, 129 contigs representing seven types of putative proteases were identified. Transcript abundance of digestive proteases and enzymatic activity assays showed that cathepsin B-like protease, cathepsin L-like protease, and serine proteases (trypsin- and chymotrypsin-like protease) were highly abundant in the gut but moderately abundant in the SG. The abundance pattern of digestive proteases in the SG and gut of E. onukii differed from that of other hemipterans, including Nilaparvata lugens, Laodelphax striatellus, Acyrthosiphum pisum, Halyomorpha halys and Nephotettix cincticeps. Phylogenetic analysis showed that aminopeptidase N-like proteins and serine proteases abundant in the SG or gut of hemipterans formed two distinct clusters. CONCLUSIONS: Altogether, this study provides insightful information on the digestive system of E. onukii. Compared to five other hemipteran species, we observed different patterns of proteases abundant in the SG and gut of E. onukii. These results will be beneficial in understanding the interaction between tea plants and E. onukii.

A Review on Different Kinds of Artificial Intelligence Solutions in TCM Syndrome Differentiation Application.

In 1979, the first computer program for TCM diagnosis was launched, although this time was about 30 years after artificial intelligence (AI) came into being and began to be widely used. However, an endless stream of artificial intelligence methods was applied in the field of Chinese medicine research, expert system, artificial neural network, data mining, and multivariate analysis; not limited to what was mentioned, this study tried to make a review on application of AI to TCM syndrome differentiation, while summarizing the artificial intelligence application of TCM syndrome differentiation in the current context. It also provides a theoretical background for the upcoming fully automated research on TCM syndrome differentiation and diagnosis robot.

Lightweight and Hydrophobic Three-Dimensional Wood-Derived Anisotropic Magnetic Porous Carbon for Highly Efficient Electromagnetic Interference Shielding.

Constructing multifunctional characteristics toward advanced electromagnetic interference shielding materials in harsh environments has become a development trend. Herein, the wood-derived magnetic porous carbon composites with a highly ordered anisotropic porous architecture were successfully fabricated through a pyrolysis procedure. The three-dimensional porous skeleton inherited from the wood stock serves as an electrically conductive network and incorporates magnetic Ni nanoparticles homogeneously and firmly embedded within the carbon matrix that can further improve the electromagnetic attenuation capacity. The optimized Ni/porous carbon (PC) composite exhibits an exceptional electromagnetic interference (EMI) shielding effectiveness of 50.8 dB at the whole X band (8.2-12.4 GHz) with a low thickness (2 mm) and an ultralow density (0.288 g/cm3) and simultaneously possesses an extraordinary compressive strength (11.7 MPa) and a hydrophobic water contact angle (152.1°). Our study provides an alternative strategy to utilize green wood-based materials to design multifunctional EMI shielding composites.

A Multicenter Randomized Controlled Pilot Trial Testing the Efficacy and Safety of Pterygopalatine Fossa Puncture Using One Acupuncture Needle for Moderate-to-Severe Persistent Allergic Rhinitis.

OBJECTIVE: To compare the efficacy and safety of pterygopalatine fossa puncture using one acupuncture needle inserted through the temporal fossa (intervention) and Chinese verum acupuncture (VA) in patients with moderate-to-severe persistent allergic rhinitis. METHODS: The patients were randomized to an intervention group receiving pterygopalatine fossa puncture with one acupuncture needle for 4 weeks (once or twice weekly, 4-8 sessions in total, with a second course performed if required) or to a control group receiving individualized VA for 4 weeks (twice weekly, eight sessions in total). Patients were followed up 4 weeks later. RESULTS: Ninety-six participants were assigned to intervention (n = 48) or VA (n = 48) or VA (P > 0.05 in all cases). Compared with the VA, the time to onset of effect in the intervention group was shorter and the duration of effectiveness was longer. The mean clinical waiting time was significantly shorter in the intervention group than in the control group (6.640 ± 3.035 min and 31.19 ± 10.216 min, respectively). The total number of sessions in the VA group was 384; 7 episodes of subcutaneous bleeding occurred but did not require treatment. The total number of sessions in the intervention group was 185. Two cases of subcutaneous bleeding (one of local hematoma during the intervention and the other one of bruising in the palpebra inferior on the day after intervention) resolved upon withdrawal from the study. CONCLUSIONS: Pterygopalatine fossa puncture using one acupuncture needle resulted in a shorter time to onset of effect, a longer duration of effectiveness, and less clinical waiting time when compared with VA. Though the significant differences for TNSS and TNNSS were shown within intervention and VA groups, there were no differences between the two groups. Although the rate of subcutaneous bleeding was low, these adverse events may influence patient compliance. This trial is registered with ISRCTN21980724.

Effect of acrylamide on glucose homeostasis in female rats and its mechanisms.

Acrylamide (AA), a food contaminant, caused islet remodeling and increased hepatic glycogen content in male rats, but the effect of AA on glucose homeostasis in female rats remains unclear. In this study, female SD rats were orally treated with 0, 15, or 30 mg/kg·bw AA for 3 weeks. The levels of fasting blood glucose (FBG), blood glucose after oral administration of glucose, plasma insulin and hepatic glycogen were measured. The histology of the pancreas was observed, and the transcription of key genes involved in glucose metabolism and insulin signaling in liver were determined. Compared with the control, exposure to 30 mg/kg·bw of AA significantly increased FBG level, reduced hepatic glycogen content and impaired glucose tolerance. Moreover, damaged islets were observed at 15 and 30 mg/kg·bw AA-exposed groups. In addition, AA exposure significantly promoted gluconeogenesis and glycogenolysis (up-regulation of pc, g6p and gp) and decreased glycolysis (down-regulation of gck and pfk). Alternations in these processes may be associated with decreased plasma insulin levels and inhibited insulin-regulated IRS/PI3K/Akt/Foxo1 signaling transduction under AA exposure. Overall, our findings demonstrated that AA disrupted glucose homeostasis and elevated FBG level in female rats possibly by interfering with glucose metabolism and hampering the physiological effect of insulin.

Structural features of LC8-induced self-association of swallow.

Cell functions depend on the collective activity of protein networks within which a few proteins, called hubs, participate in a large number of interactions. Dynein light chain LC8, first discovered as a subunit of the motor protein dynein, is considered to have a role broader than that of dynein, and its participation in diverse systems fits the description of a hub. Among its partners is Swallow with which LC8 is essential for proper localization of bicoid mRNA at the anterior cortex of Drosophila oocytes. Why LC8 is essential in this process is not clear, but emerging evidence suggests that LC8 functions by promoting self-association and/or structural organization of its diverse binding partners. This work addresses the energetics and structural features of LC8-induced Swallow self-association distant from LC8 binding. Mutational design based on a hypothetical helical wheel, intermonomer nuclear Overhauser effects assigned to residues expected at interface positions, and circular dichroism spectral characteristics indicate that the LC8-promoted dimer of Swallow is a coiled coil. Secondary chemical shifts and (15)N backbone relaxation identify the boundaries and distinguishing structural features of the coiled coil. Thermodynamic analysis of Swallow polypeptides designed to decouple self-association from LC8 binding reveals that the higher binding affinity of the engineered bivalent Swallow is of purely entropic origin and that the linker separating the coiled coil from the LC8 binding site remains disordered. We speculate that the LC8-promoted coiled coil is critical for bicoid mRNA localization because it favors structural organization of Swallow, which except for the central LC8-promoted coiled coil is primarily disordered.

Multiple recognition motifs in nucleoporin Nup159 provide a stable and rigid Nup159-Dyn2 assembly.

Dyn2 is the yeast ortholog of the molecular hub LC8, which binds disordered proteins and promotes their self-association and higher order assembly. Dyn2 is proposed to dimerize and stabilize the Nup82-Nsp1-Nup159 complex of the nuclear pore assembly through its interaction with nucleoporin Nup159. Nup159 has six LC8 recognition motifs separated by short linkers. NMR experiments reported here show that the Dyn2 binding domain of Nup159 is intrinsically disordered and that binding of one equivalent of Dyn2 dimer aligns two Nup159 chains along the full Dyn2 binding domain to form a bivalent scaffold that promotes binding of other Dyn2 dimers. Isothermal titration calorimetry of Dyn2 binding to Nup constructs of increasing lengths determine that the third LC8 recognition motifs does not bind Dyn2. A new approach to identifying active LC8 recognition motifs based on NMR-detected ß-sheet propensities is presented. Isothermal titration calorimetry experiments also show that, due to unfavorable entropy changes, a Nup-Dyn2 complex with three Dyn2 dimers is more stable than the wild-type complex with five Dyn2 dimers. The calorimetric results argue that, from a thermodynamics perspective, only three Dyn2 dimers are needed for optimal stability and suggest that the evolutionary adaptation of multiple tandem LC8 recognition motifs imparts to the complex other properties such as rigidity and a kink in the rod-like structure. These findings extend the repertoire of functions of intrinsically disordered protein to fine-tuning and versatile assembly of higher order macromolecular complexes.

Intrinsic disorder in dynein intermediate chain modulates its interactions with NudE and dynactin.

The functional diversity of cytoplasmic dynein is in part attributed to multiple interactions between noncatalytic dynein subunits and an array of regulatory proteins. This study focuses on the interaction between the dynein intermediate chain subunit (IC) and a dynein regulator protein (NudE). We use isothermal titration calorimetry and NMR spectroscopy to map their interacting sections to their respective N-terminal domains, which are predicted to form dimeric coiled-coils. Interestingly, the specific residues within IC that interact with NudE are a subset of the bi-segmental binding region reported for p150(Glued), a subunit of the dynein activator protein dynactin. Although the IC binding domains of both NudE and p150(Glued) form dimeric coiled-coils and bind IC at a common site, we observe distinct binding modes for each regulatory protein: 1) NudE binds region 1 of the bi-segmental binding footprint of p150(Glued), whereas p150(Glued) requires regions 1 and 2 to match the binding affinity of NudE with region 1 alone. 2) Compared with unbound IC, NudE-bound IC shows a slight increase in flexibility in region 2, in contrast to the increase in ordered structure observed for p150(Glued)-bound IC (Morgan, J. L., Song, Y., and Barbar, E. (2011) J. Biol. Chem. 286, 39349-39359). 3) Although NudE has a higher affinity for the common binding segment on IC, when all three proteins are in solution, IC preferentially binds p150(Glued). These results underscore the importance of a bi-segmental binding region of IC and disorder in region 2 and flanking linkers in selecting which regulatory protein binds IC.

Structural dynamics and multiregion interactions in dynein-dynactin recognition.

Cytoplasmic dynein is a 1.2-MDa multisubunit motor protein complex that, together with its activator dynactin, is responsible for the majority of minus end microtubule-based motility. Dynactin targets dynein to specific cellular locations, links dynein to cargo, and increases dynein processivity. These two macromolecular complexes are connected by a direct interaction between dynactin's largest subunit, p150(Glued), and dynein intermediate chain (IC) subunit. Here, we demonstrate using NMR spectroscopy and isothermal titration calorimetry that the binding footprint of p150(Glued) on IC involves two noncontiguous recognition regions, and both are required for full binding affinity. In apo-IC, the helical structure of region 1, the nascent helix of region 2, and the disorder in the rest of the chain are determined from coupling constants, amide-amide sequential NOEs, secondary chemical shifts, and various dynamics measurements. When bound to p150(Glued), different patterns of spectral exchange broadening suggest that region 1 forms a coiled-coil and region 2 a packed stable helix, with the intervening residues remaining disordered. In the 150-kDa complex of p150(Glued), IC, and two light chains, the noninterface segments remain disordered. The multiregion IC binding interface, the partial disorder of region 2 and its potential for post-translational modification, and the modulation of the length of the longer linker by alternative splicing may provide a basis for elegant and multifaceted regulation of binding between IC and p150(Glued). The long disordered linker between the p150(Glued) binding segments and the dynein light chain consensus sequences could also provide an attractive recognition platform for diverse cargoes.

The crystal structure of dynein intermediate chain-light chain roadblock complex gives new insights into dynein assembly.

The roadblock/LC7 dynein light chain is a ubiquitous component of all dyneins and is essential for many diverse processes including proper axonal transport and dendrite growth. In addition, LC7 functions in non-dynein transcriptional activation of the transforming growth factor-beta complex. Crystal structures of Drosophila melanogaster LC7 in the apo form and in complex with a segment of the disordered N-terminal domain of dynein intermediate chain (IC) provide the first definitive identification of the IC sequence recognized by LC7. The site, confirmed by isothermal titration calorimetry studies, overlaps the IC sequence considered in the literature to be an IC self-association domain. The IC peptide binds as two amphipathic helices that lie along an extensive hydrophobic cleft on LC7 and ends with a polar side-chain interaction network that includes conserved residues from both proteins. The LC7 recognition sequence on IC and its interface with LC7 are well conserved and are, thus, likely representative of all IC x LC7 structures. Interestingly, the position of bound IC in the IC x LC7 complex mimics a helix that is integrated into the primary structure in distantly related LC7 homologs. The IC x LC7 structure further shows that the naturally occurring robl(Z) deletion mutation contains the majority of the IC binding site and suggests that promotion of IC binding by phosphorylation of LC7 is an indirect effect.

Detection of the TCDD binding-fingerprint within the Ah receptor ligand binding domain by structurally driven mutagenesis and functional analysis.

The aryl hydrocarbon receptor (AhR) is a ligand-dependent, basic helix-loop-helix Per-Arnt-Sim (PAS)-containing transcription factor that can bind and be activated by structurally diverse chemicals, including the toxic environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Our previous three-dimensional homology model of the mouse AhR (mAhR) PAS B ligand binding domain allowed identification of the binding site and its experimental validation. We have extended this analysis by conducting comparative structural modeling studies of the ligand binding domains of six additional high-affinity mammalian AhRs. These results, coupled with site-directed mutagenesis and AhR functional analysis, have allowed detection of the "TCDD binding-fingerprint" of conserved residues within the ligand binding cavity necessary for high-affinity TCDD binding and TCDD-dependent AhR transformation DNA binding. The essential role of selected residues was further evaluated using molecular docking simulations of TCDD with both wild-type and mutant mAhRs. Taken together, our results dramatically improve our understanding of the molecular determinants of TCDD binding and provide a basis for future studies directed toward rationalizing the observed species differences in AhR sensitivity to TCDD and understanding the mechanistic basis for the dramatic diversity in AhR ligand structure.