Engineering the Strain and Interlayer Excitons of 2D Materials via Lithographically Engraved Hexagonal Boron Nitride.

Strain engineering has quickly emerged as a viable option to modify the electronic, optical, and magnetic properties of 2D materials. However, it remains challenging to arbitrarily control the strain. Here we show that, by creating atomically flat surface nanostructures in hexagonal boron nitride, we achieve an arbitrary on-chip control of both the strain distribution and magnitude on high-quality molybdenum disulfide. The phonon and exciton emissions are shown to vary in accordance with our strain field designs, enabling us to write and draw any photoluminescence color image in a single chip. Moreover, our strain engineering offers a powerful means to significantly and controllably alter the strengths and energies of interlayer excitons at room temperature. This method can be easily extended to other material systems and offers promise for functional excitonic devices.

Postexercise muscle glycogen synthesis with glucose, galactose, and combined galactose-glucose ingestion.

Ingested galactose can enhance postexercise liver glycogen repletion when combined with glucose but effects on muscle glycogen synthesis are unknown. In this double-blind randomized study participants [7 men and 2 women; V̇o2max: 51.1 (8.7) mL·kg-1·min-1] completed three trials of exhaustive cycling exercise followed by a 4-h recovery period, during which carbohydrates were ingested at the rate of 1.2 g·kg-1·h-1 comprising glucose (GLU), galactose (GAL) or galactose + glucose (GAL + GLU; 1:2 ratio). The increase in vastus lateralis skeletal-muscle glycogen concentration during recovery was higher with GLU relative to GAL + GLU [contrast: +50 mmol·(kg DM)-1; 95%CL 10, 89; P = 0.021] and GAL [+46 mmol·(kg DM)-1; 95%CL 8, 84; P = 0.024] with no difference between GAL + GLU and GAL [-3 mmol·(kg DM)-1; 95%CL -44, 37; P = 0.843]. Plasma glucose concentration in GLU was not significantly different vs. GAL + GLU (+ 0.41 mmol·L-1; 95%CL 0.13, 0.94) but was significantly lower than GAL (-0.75 mmol·L-1; 95%CL -1.34, -0.17) and also lower in GAL vs. GAL + GLU (-1.16 mmol·-1; 95%CL -1.80, -0.53). Plasma insulin was higher in GLU + GAL and GLU compared with GAL but not different between GLU + GAL and GLU. Plasma galactose concentration was higher in GAL compared with GLU (3.35 mmol·L-1; 95%CL 3.07, 3.63) and GAL + GLU (3.22 mmol·L-1; 95%CL 3.54, 2.90) with no difference between GLU + GAL (0.13 mmol·L-1; 95%CL -0.11, 0.37) and GLU. Compared with galactose or a galactose + glucose blend, glucose feeding was more effective in postexercise muscle glycogen synthesis. Comparable muscle glycogen synthesis was observed with galactose-glucose coingestion and exclusive galactose-only ingestion.NEW & NOTEWORTHY Postexercise galactose-glucose coingestion or exclusive galactose-only ingestion resulted in a lower rate of skeletal-muscle glycogen replenishment compared with exclusive glucose-only ingestion. Comparable muscle glycogen synthesis was observed with galactose-glucose coingestion and exclusive galactose-only ingestion.

Chiral Binaphthalene Building Blocks for Self-Assembled Nanoscale CPL Emitters.

The introduction of biuret hydrogen-bonding sites onto chiral binaphthalene-based chromophores was investigated as a route to sub-micron-sized, vesicle-like aggregates endowed with chiroptical properties. The synthesis was conducted from the corresponding chiral 4,4'-dibromo-1,1'-bis(2-naphthol) via Suzuki-Miyaura coupling to afford luminescent chromophores whose emission spectrum could be tuned from blue to yellow-green through extension of the conjugation. For all compounds, the spontaneous formation of hollow spheres with a diameter of ca. 200-800 nm was evidenced by scanning electron microscopy, along with strong asymmetry in the circularly polarized absorption spectra. For some compounds, the emission also displayed circular polarization with values of glum = ca. 10-3 which could be increased upon aggregation.

Ubiquitin E3 ligase Atrogin-1 protein is regulated via the rapamycin-sensitive mTOR-S6K1 signaling pathway in C2C12 muscle cells.

Atrogin-1 and Muscle-specific RING finger protein 1 (MuRF1) are highly expressed in multiple conditions of skeletal muscle atrophy. The phosphoinositide 3-kinase (PI3K)/Akt/forkhead box (FoxO) signaling pathway is well known to regulate Atrogin-1 and MuRF1 gene expressions. However, Akt activation also activates the mechanistic target of rapamycin complex 1 (mTORC1), which induces skeletal muscle hypertrophy. Whether mTORC1-dependent signaling has a role in regulating Atrogin-1 and/or MuRF1 gene and protein expression is currently unclear. In this study, we showed that activation of insulin-mediated Akt signaling suppresses both Atrogin-1 and MuRF1 protein contents and that inhibition of Akt increases both Atrogin-1 and MuRF1 protein contents in C2C12 myotubes. Interestingly, inhibition of mTORC1 with a specific mTORC1 inhibitor, rapamycin, increased Atrogin-1, but not MuRF1, protein content. Furthermore, activation of AMP-activated protein kinase (AMPK), a negative regulator of the mTORC1 signaling pathway, also showed distinct time-dependent changes between Atrogin-1 and MuRF1 protein contents, suggesting differential regulatory mechanisms between Atrogin-1 and MuRF1 protein content. To further explore the downstream of mTORC1 signaling, we employed a specific S6K1 inhibitor, PF-4708671. We found that Atrogin-1 protein content was dose-dependently increased with PF-4708671 treatment, whereas MuRF1 protein content was decreased at 50 µM of PF-4708671 treatment. However, MuRF1 protein content was unexpectedly increased by PF-4708671 treatment for a longer period. Overall, our results indicate that Atrogin-1 and MuRF1 protein contents are regulated by different mechanisms, the downstream of Akt, and that Atrogin-1 protein content can be regulated by the rapamycin-sensitive mTOR-S6K1-dependent signaling pathway.

Quantifying excess deaths among solid organ transplant recipients in the COVID-19 era.

Estimating the total coronavirus disease 2019 (COVID-19) mortality burden of solid organ transplant recipients (SOTRs), both directly through COVID-19 infection and indirectly through other impacts on the healthcare system and society, is critical for understanding the disease's impact on the SOTR population. Using SRTR data, we modeled expected mortality risk per month pre-COVID (January 2015-February 2020) for kidney/liver/heart/lung SOTRs, and compared monthly COVID-era deaths (March 2020-March 2021) to expected rates, overall and among subgroups. Deaths above expected rates were designated "excess deaths." Between March 2020 and March 2021, there were 3739/827/265/252 excess deaths among kidney/liver/heart/lung SOTRs, respectively, representing a 41.2%/27.4%/18.5%/15.0% increase above expected deaths. 93.0% of excess deaths occurred in patients age≥50. The observed:expected ratio was highest among Hispanic SOTRs (1.82) and lowest among White SOTRs (1.20); 56.0% of excess deaths occurred among Black or Hispanic SOTRs. 64.7% of excess deaths occurred among patients who had survived ≥5 years post-transplant. Excess deaths peaked in January 2021; geographic distribution of excess deaths broadly mirrored COVID-19 incidence. COVID-19 likely caused over 5000 excess deaths among SOTRs in the US in a 13-month period, representing 1 in 75 SOTRs and a substantial proportion of all deaths among SOTRs during this time. SOTRs will remain at elevated mortality risk until the COVID-19 pandemic can be controlled.

Recent advances in measuring and understanding the regulation of exercise-mediated protein degradation in skeletal muscle.

Skeletal muscle protein turnover plays a crucial role in controlling muscle mass and protein quality control, including sarcomeric (structural and contractile) proteins. Protein turnover is a dynamic and continual process of protein synthesis and degradation. The ubiquitin proteasome system (UPS) is a key degradative system for protein degradation and protein quality control in skeletal muscle. UPS-mediated protein quality control is known to be impaired in aging and diseases. Exercise is a well-recognized, nonpharmacological approach to promote muscle protein turnover rates. Over the past decades, we have acquired substantial knowledge of molecular mechanisms of muscle protein synthesis after exercise. However, there have been considerable gaps in the mechanisms of how muscle protein degradation is regulated at the molecular level. The main challenge to understand muscle protein degradation is due in part to the lack of solid stable isotope tracer methodology to measure muscle protein degradation rate. Understanding the mechanisms of UPS with the concomitant measurement of protein degradation rate in skeletal muscle will help identify novel therapeutic strategies to ameliorate impaired protein turnover and protein quality control in aging and diseases. Thus, the goal of this present review was to highlight how recent advances in the field may help improve our understanding of exercise-mediated protein degradation. We discuss 1) the emerging roles of protein phosphorylation and ubiquitylation modifications in regulating proteasome-mediated protein degradation after exercise and 2) methodological advances to measure in vivo myofibrillar protein degradation rate using stable isotope tracer methods.

Cyano Derivatives of 7-Aminoquinoline That Are Highly Emissive in Water: Potential for Sensing Applications.

6-Cyano-7-aminoquinoline (6CN-7AQ) and 3-cyano-7-aminoquinoline (3CN-7AQ) were synthesized and found to exhibit intense emission with quantum yield as high as 63 % and 85 %, respectively, in water. Conversely, their derivatives 6-cyano-7-azidoquinoline (6CN-7N3 Q) and 3-cyano-7-azidoquinoline (3CN-7N3 Q) show virtually no emission, which makes them suitable to be used as recognition agents in azide reactions based on fluorescence recovery. Moreover, conjugation of 6CN-7AQ with a hydrophobic biomembrane-penetration peptide PFVYLI renders a nearly non-emissive 6CN-7AQ-PFVYLI composite, which can be digested by proteinase K, recovering the highly emissive 6CN-7AQ with ∼200-fold enhancement. The result provides an effective early confirmation for RT-qPCR in viral detection.

AMPK activation induces mitophagy and promotes mitochondrial fission while activating TBK1 in a PINK1-Parkin independent manner.

Mitophagy is a key process regulating mitochondrial quality control. Several mechanisms have been proposed to regulate mitophagy, but these have mostly been studied using stably expressed non-native proteins in immortalized cell lines. In skeletal muscle, mitophagy and its molecular mechanisms require more thorough investigation. To measure mitophagy directly, we generated a stable skeletal muscle C2C12 cell line, expressing a mitophagy reporter construct (mCherry-green fluorescence protein-mtFIS1101-152 ). Here, we report that both carbonyl cyanide m-chlorophenyl hydrazone (CCCP) treatment and adenosine monophosphate activated protein kinase (AMPK) activation by 991 promote mitochondrial fission via phosphorylation of MFF and induce mitophagy by ~20%. Upon CCCP treatment, but not 991, ubiquitin phosphorylation, a read-out of PTEN-induced kinase 1 (PINK1) activity, and Parkin E3 ligase activity toward CDGSH iron sulfur domain 1 (CISD1) were increased. Although the PINK1-Parkin signaling pathway is active in response to CCCP treatment, we observed no change in markers of mitochondrial protein content. Interestingly, our data shows that TANK-binding kinase 1 (TBK1) phosphorylation is increased after both CCCP and 991 treatments, suggesting TBK1 activation to be independent of both PINK1 and Parkin. Finally, we confirmed in non-muscle cell lines that TBK1 phosphorylation occurs in the absence of PINK1 and is regulated by AMPK-dependent signaling. Thus, AMPK activation promotes mitophagy by enhancing mitochondrial fission (via MFF phosphorylation) and autophagosomal engulfment (via TBK1 activation) in a PINK1-Parkin independent manner.

PINK1-dependent phosphorylation of Serine111 within the SF3 motif of Rab GTPases impairs effector interactions and LRRK2-mediated phosphorylation at Threonine72.

Loss of function mutations in the PTEN-induced kinase 1 (PINK1) kinase are causal for autosomal recessive Parkinson's disease (PD) whilst gain of function mutations in the LRRK2 kinase cause autosomal dominant PD. PINK1 indirectly regulates the phosphorylation of a subset of Rab GTPases at a conserved Serine111 (Ser111) residue within the SF3 motif. Using genetic code expansion technologies, we have produced stoichiometric Ser111-phosphorylated Rab8A revealing impaired interactions with its cognate guanine nucleotide exchange factor and GTPase activating protein. In a screen for Rab8A kinases we identify TAK1 and MST3 kinases that can efficiently phosphorylate the Switch II residue Threonine72 (Thr72) in a similar manner as LRRK2 in vitro. Strikingly, we demonstrate that Ser111 phosphorylation negatively regulates the ability of LRRK2 but not MST3 or TAK1 to phosphorylate Thr72 of recombinant nucleotide-bound Rab8A in vitro and demonstrate an interplay of PINK1- and LRRK2-mediated phosphorylation of Rab8A in transfected HEK293 cells. Finally, we present the crystal structure of Ser111-phosphorylated Rab8A and nuclear magnetic resonance structure of Ser111-phosphorylated Rab1B. The structures reveal that the phosphorylated SF3 motif does not induce any major changes, but may interfere with effector-Switch II interactions through intramolecular H-bond formation and/or charge effects with Arg79. Overall, we demonstrate antagonistic regulation between PINK1-dependent Ser111 phosphorylation and LRRK2-mediated Thr72 phosphorylation of Rab8A indicating a potential cross-talk between PINK1-regulated mitochondrial homeostasis and LRRK2 signalling that requires further investigation in vivo.

AIoT-Enabled Rehabilitation Recognition System-Exemplified by Hybrid Lower-Limb Exercises.

Ubiquitous health management (UHM) is vital in the aging society. The UHM services with artificial intelligence of things (AIoT) can assist home-isolated healthcare in tracking rehabilitation exercises for clinical diagnosis. This study combined a personalized rehabilitation recognition (PRR) system with the AIoT for the UHM of lower-limb rehabilitation exercises. The three-tier infrastructure integrated the recognition pattern bank with the sensor, network, and application layers. The wearable sensor collected and uploaded the rehab data to the network layer for AI-based modeling, including the data preprocessing, featuring, machine learning (ML), and evaluation, to build the recognition pattern. We employed the SVM and ANFIS methods in the ML process to evaluate 63 features in the time and frequency domains for multiclass recognition. The Hilbert-Huang transform (HHT) process was applied to derive the frequency-domain features. As a result, the patterns combining the time- and frequency-domain features, such as relative motion angles in y- and z-axis, and the HHT-based frequency and energy, could achieve successful recognition. Finally, the suggestive patterns stored in the AIoT-PRR system enabled the ML models for intelligent computation. The PRR system can incorporate the proposed modeling with the UHM service to track the rehabilitation program in the future.

Global Deletion of 11ß-HSD1 Prevents Muscle Wasting Associated with Glucocorticoid Therapy in Polyarthritis.

Glucocorticoids provide indispensable anti-inflammatory therapies. However, metabolic adverse effects including muscle wasting restrict their use. The enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) modulates peripheral glucocorticoid responses through pre-receptor metabolism. This study investigates how 11ß-HSD1 influences skeletal muscle responses to glucocorticoid therapy for chronic inflammation. We assessed human skeletal muscle biopsies from patients with rheumatoid arthritis and osteoarthritis for 11ß-HSD1 activity ex vivo. Using the TNF-α-transgenic mouse model (TNF-tg) of chronic inflammation, we examined the effects of corticosterone treatment and 11ß-HSD1 global knock-out (11ßKO) on skeletal muscle, measuring anti-inflammatory gene expression, muscle weights, fiber size distribution, and catabolic pathways. Muscle 11ß-HSD1 activity was elevated in patients with rheumatoid arthritis and correlated with inflammation markers. In murine skeletal muscle, glucocorticoid administration suppressed IL6 expression in TNF-tg mice but not in TNF-tg11ßKO mice. TNF-tg mice exhibited reductions in muscle weight and fiber size with glucocorticoid therapy. In contrast, TNF-tg11ßKO mice were protected against glucocorticoid-induced muscle atrophy. Glucocorticoid-mediated activation of catabolic mediators (FoxO1, Trim63) was also diminished in TNF-tg11ßKO compared to TNF-tg mice. In summary, 11ß-HSD1 knock-out prevents muscle atrophy associated with glucocorticoid therapy in a model of chronic inflammation. Targeting 11ß-HSD1 may offer a strategy to refine the safety of glucocorticoids.

Tuning the Circular Dichroism and Circular Polarized Luminescence Intensities of Chiral 2D Hybrid Organic-Inorganic Perovskites through Halogenation of the Organic Ions.

Through the incorporation of various halogen-substituted chiral organic cations, the effects of chiral molecules on the chiroptical properties of hybrid organic-inorganic perovskites (HOIPs) are investigated. Among them, the HOIP having a Cl-substituted chiral cation exhibits the highest circular dichroism (CD) and circular polarized luminescence (CPL) intensities, indicating the existence of the largest rotatory strength, whereas the F-substituted HIOP shows the weakest intensities. The observed modulation can be correlated to the varied magnetic transition dipole of HOIPs, which is sensitive to the d-spacing between inorganic layers and the halogen-halogen interaction between organic cations and the inorganic sheets. These counteracting effects meet the optimal CD and CPL intensity with chlorine substitution, rendering the rotatory strength of HOIPs arranged in the order of (ClMBA)2 PbI4 >(BrMBA)2 PbI4 >(IMBA)2 PbI4 >(MBA)2 PbI4 >(FMBA)2 PbI4 .

Early impact of COVID-19 on transplant center practices and policies in the United States.

COVID-19 is a novel, rapidly changing pandemic: consequently, evidence-based recommendations in solid organ transplantation (SOT) remain challenging and unclear. To understand the impact on transplant activity across the United States, and center-level variation in testing, clinical practice, and policies, we conducted a national survey between March 24, 2020 and March 31, 2020 and linked responses to the COVID-19 incidence map. Response rate was a very high 79.3%, reflecting a strong national priority to better understand COVID-19. Complete suspension of live donor kidney transplantation was reported by 71.8% and live donor liver by 67.7%. While complete suspension of deceased donor transplantation was less frequent, some restrictions to deceased donor kidney transplantation were reported by 84.0% and deceased donor liver by 73.3%; more stringent restrictions were associated with higher regional incidence of COVID-19. Shortage of COVID-19 tests was reported by 42.5%. Respondents reported a total of 148 COVID-19 recipients from <1 to >10 years posttransplant: 69.6% were kidney recipients, and 25.0% were critically ill. Hydroxychloroquine (HCQ) was used by 78.1% of respondents; azithromycin by 46.9%; tocilizumab by 31.3%, and remdesivir by 25.0%. There is wide heterogeneity in center-level response across the United States; ongoing national data collection, expert discussion, and clinical studies are critical to informing evidence-based practices.

Transmastoid presigmoid retrolabyrinthine approach for removal of pontine cavernous malformation: how I do it.

BACKGROUND: Bleeding of brainstem cavernous malformations (BSCM) cause high morbidity and should be treated surgically whenever possible. METHOD: We present a 56-year-old man, who was diagnosed with a BSCM at right pons, which caused functional impairments of dorsal column, spinothalamic tract, cochlear nucleus, and middle cerebellar peduncle. A transmastoid presigmoid retorlabyrinthine approach via the lateral pontine zone (LPZ), with an assistance of imaging guidance and intraoperative neurophysiological monitoring, was performed to completely resect the BSCM. The patient recovered despite a transient worsening of cerebellar sign and hemiparesthesia for 1 week, without surgical complications. CONCLUSIONS: A transmastoid presigmoid retrolabyrinthine approach through LPZ is safe and effective for lateral pontine BSCM resection.

Phosphoproteomic screening identifies Rab GTPases as novel downstream targets of PINK1.

Mutations in the PTEN-induced kinase 1 (PINK1) are causative of autosomal recessive Parkinson's disease (PD). We have previously reported that PINK1 is activated by mitochondrial depolarisation and phosphorylates serine 65 (Ser(65)) of the ubiquitin ligase Parkin and ubiquitin to stimulate Parkin E3 ligase activity. Here, we have employed quantitative phosphoproteomics to search for novel PINK1-dependent phosphorylation targets in HEK (human embryonic kidney) 293 cells stimulated by mitochondrial depolarisation. This led to the identification of 14,213 phosphosites from 4,499 gene products. Whilst most phosphosites were unaffected, we strikingly observed three members of a sub-family of Rab GTPases namely Rab8A, 8B and 13 that are all phosphorylated at the highly conserved residue of serine 111 (Ser(111)) in response to PINK1 activation. Using phospho-specific antibodies raised against Ser(111) of each of the Rabs, we demonstrate that Rab Ser(111) phosphorylation occurs specifically in response to PINK1 activation and is abolished in HeLa PINK1 knockout cells and mutant PINK1 PD patient-derived fibroblasts stimulated by mitochondrial depolarisation. We provide evidence that Rab8A GTPase Ser(111) phosphorylation is not directly regulated by PINK1 in vitro and demonstrate in cells the time course of Ser(111) phosphorylation of Rab8A, 8B and 13 is markedly delayed compared to phosphorylation of Parkin at Ser(65). We further show mechanistically that phosphorylation at Ser(111) significantly impairs Rab8A activation by its cognate guanine nucleotide exchange factor (GEF), Rabin8 (by using the Ser111Glu phosphorylation mimic). These findings provide the first evidence that PINK1 is able to regulate the phosphorylation of Rab GTPases and indicate that monitoring phosphorylation of Rab8A/8B/13 at Ser(111) may represent novel biomarkers of PINK1 activity in vivo. Our findings also suggest that disruption of Rab GTPase-mediated signalling may represent a major mechanism in the neurodegenerative cascade of Parkinson's disease.

Catalytic-Type Excited-State N-H Proton-Transfer Reaction in 7-Aminoquinoline and Its Derivatives.

7-Aminoquinoline (7AQ) and various amino derivatives thereof (-NHR) have been strategically designed and synthesized to study their excited-state proton-transfer (ESPT) properties. Due to the large separation between the proton donor -NHR and the acceptor -N- site, ESPT in 7AQ derivatives, if available, should proceed under protic solvent catalysis. ESPT is found to be influenced by the acidity of -NHR and the basicity of the proton-acceptor -N- in the quinoline moiety. The latter is varied by the resonance effect at the quinoline -N- site induced by the -NHR substituent. For those 7AQ derivatives undergoing ESPT, increased quinoline basicity results in a faster rate of ESPT, implying that proton donation from methanol to the quinoline moiety may serve as a key step in the process. Our studies also indicate the existence of an equilibrium between cis and trans arrangements of -NHR in terms of its hydrogen-bond (H-bond) configuration with methanol, whereby only the cis-H-bonded form undergoes methanol-assisted ESPT. With one exception, the interconversion between cis and trans configurations is much faster than the rate of ESPT, yielding amino-type (normal form) and imine-type (proton-transfer tautomer) emissions with distinct relaxation dynamics.

Characterization of Fibrinogen as a Key Modulator in Patients with Wilson's Diseases with Functional Proteomic Tools.

Wilson's disease (WD) is an autosomal recessive disorder of copper metabolism caused by defects in the ATPase gene (ATP7B). The various clinical features result from the massive accumulation of copper in the liver, cornea and basal ganglia. Although WD can be effectively treated with proper medicine, this disease is difficult to clearly diagnose due to its indefinite symptoms. In the current study, we achieved a positive correlation between clinical symptoms and the enzymatic activity of ceruloplasmin in WD patients. Furthermore, proteome profiles of plasma as well as network analysis demonstrated that fibrinogen is a critical indicator which is significantly unregulated in WD subjects in comparison to healthy donors and closely linked to pathogenesis of WD. Here, we applied 2DE-immunoblots and immunohistochemistry to verify the protein level and localization in situ. The enhanced expression of fibrinogen in the plasma of WD subjects with respect to that of healthy controls and patients with distinct disorders was also confirmed by utilizing clinical samples. As expected, application of high dose of copper induced expression of fibrinogen, while knockdown of ceruloplasmin also resulted in upregulation of fibrinogen as well as elimination of superoxide dismutase (SOD), leading to increased oxidative stress in cells. In summary, the liver injury or oxidative stress induced by the progression of WD may account for the obvious increase of fibrinogen, which in turn triggers inflammatory responses and interferes coagulation cascades; this finding sheds light on the early detection and diagnosis of WD.

Probes of ubiquitin E3 ligases enable systematic dissection of parkin activation.

E3 ligases represent an important class of enzymes, yet there are currently no chemical probes for profiling their activity. We develop a new class of activity-based probe by re-engineering a ubiquitin-charged E2 conjugating enzyme and demonstrate the utility of these probes by profiling the transthiolation activity of the RING-in-between-RING (RBR) E3 ligase parkin in vitro and in cellular extracts. Our study provides valuable insight into the roles, and cellular hierarchy, of distinct phosphorylation events in parkin activation. We also profile parkin mutations associated with patients with Parkinson's disease and demonstrate that they mediate their effect largely by altering transthiolation activity. Furthermore, our probes enable direct and quantitative measurement of endogenous parkin activity, revealing that endogenous parkin is activated in neuronal cell lines (≥75%) in response to mitochondrial depolarization. This new technology also holds promise as a novel biomarker of PINK1-parkin signaling, as demonstrated by its compatibility with samples derived from individuals with Parkinson's disease.

Benzimidazole derivative small-molecule 991 enhances AMPK activity and glucose uptake induced by AICAR or contraction in skeletal muscle.

AMP-activated protein kinase (AMPK) plays diverse roles and coordinates complex metabolic pathways for maintenance of energy homeostasis. This could be explained by the fact that AMPK exists as multiple heterotrimer complexes comprising a catalytic α-subunit (α1 and α2) and regulatory ß (ß1 and ß2)- and γ (γ1, γ2, γ3)-subunits, which are uniquely distributed across different cell types. There has been keen interest in developing specific and isoform-selective AMPK-activating drugs for therapeutic use and also as research tools. Moreover, establishing ways of enhancing cellular AMPK activity would be beneficial for both purposes. Here, we investigated if a recently described potent AMPK activator called 991, in combination with the commonly used activator 5-aminoimidazole-4-carboxamide riboside or contraction, further enhances AMPK activity and glucose transport in mouse skeletal muscle ex vivo. Given that the γ3-subunit is exclusively expressed in skeletal muscle and has been implicated in contraction-induced glucose transport, we measured the activity of AMPKγ3 as well as ubiquitously expressed γ1-containing complexes. We initially validated the specificity of the antibodies for the assessment of isoform-specific AMPK activity using AMPK-deficient mouse models. We observed that a low dose of 991 (5 µM) stimulated a modest or negligible activity of both γ1- and γ3-containing AMPK complexes. Strikingly, dual treatment with 991 and 5-aminoimidazole-4-carboxamide riboside or 991 and contraction profoundly enhanced AMPKγ1/γ3 complex activation and glucose transport compared with any of the single treatments. The study demonstrates the utility of a dual activator approach to achieve a greater activation of AMPK and downstream physiological responses in various cell types, including skeletal muscle.