Regulation of GTPase function by autophosphorylation.

A unifying feature of the RAS superfamily is a conserved GTPase cycle by which these proteins transition between active and inactive states. We demonstrate that autophosphorylation of some GTPases is an intrinsic regulatory mechanism that reduces nucleotide hydrolysis and enhances nucleotide exchange, altering the on/off switch that forms the basis for their signaling functions. Using X-ray crystallography, nuclear magnetic resonance spectroscopy, binding assays, and molecular dynamics on autophosphorylated mutants of H-RAS and K-RAS, we show that phosphoryl transfer from GTP requires dynamic movement of the switch II region and that autophosphorylation promotes nucleotide exchange by opening the active site and extracting the stabilizing Mg2+. Finally, we demonstrate that autophosphorylated K-RAS exhibits altered effector interactions, including a reduced affinity for RAF proteins in mammalian cells. Thus, autophosphorylation leads to altered active site dynamics and effector interaction properties, creating a pool of GTPases that are functionally distinct from their non-phosphorylated counterparts.

Changes in Inflammatory Markers in Patients Treated for Buruli Ulcer and Their Ability to Predict Paradoxical Reactions.

Mycobacterium ulcerans causes Buruli ulcer, the third most frequent mycobacterial disease after tuberculosis and leprosy. Transient clinical deteriorations, known as paradoxical reactions (PRs), occur in some patients during or after antibiotic treatment. We investigated the clinical and biological features of PRs in a prospective cohort of 41 patients with Buruli ulcer from Benin. Neutrophil counts decreased from baseline to day 90, and interleukin 6 (IL-6), granulocyte colony-stimulating factor, and vascular endothelial growth factor were the cytokines displaying a significant monthly decrease relative to baseline. PRs occurred in 10 (24%) patients. The baseline biological and clinical characteristics of the patients presenting with PRs did not differ significantly from those of the other patients. However, the patients with PRs had significantly higher IL-6 and tumor necrosis factor alpha (TNF-α) concentrations on days 30, 60, and 90 after the start of antibiotic treatment. The absence of a decrease in IL-6 and TNF-α levels during treatment should alert clinicians to the possibility of PR onset.

The emergence of regenerative medicine in organ transplantation: 1st European Cell Therapy and Organ Regeneration Section meeting.

Regenerative medicine is emerging as a novel field in organ transplantation. In September 2019, the European Cell Therapy and Organ Regeneration Section (ECTORS) of the European Society for Organ Transplantation (ESOT) held its first meeting to discuss the state-of-the-art of regenerative medicine in organ transplantation. The present article highlights the key areas of interest and major advances in this multidisciplinary field in organ regeneration and discusses its implications for the future of organ transplantation.

Craniofacial characterization of Marfan Syndrome.

OBJECTIVE: The morbidity and mortality associated with the Marfan Syndrome (MFS) warrant timely diagnosis and intervention that can improve long-term prognosis. The aim of this study was to test the hypothesis that a distinct craniofacial morphology exists for patients with MFS that can be described quantitatively and qualitatively. METHODS: Subjects with a positive diagnosis of MFS were recruited for this study (N = 36). Craniofacial anthropometric measurements were made on each subject and compared to established norms of age- and sex-matched controls using z-scores calculated for measurements of MFS patients. Lateral and frontal photographs were obtained to make qualitative assessments and describe facial features of subjects, and a clinical examination was completed to document occlusal relationships. RESULTS: The subjects were primarily female (58%) ranging in age between 4 and 57 years (mean age 10.7 ± 6.0 years). Comparison of craniofacial measurements revealed that for 10 of the 12 measurements, ≥65% of the study population had a z-score of ± 2 and fell within the normal range for facial dimension. For 2 of the 12 measurements, over half of the subjects fell outside of the normal range (z-score < -2 or > 2) for facial dimension. Specifically, the majority of participants resided in the supernormal category for biocular width and the subnormal category for width of the face. Photographic assessment revealed retrognathia (54%) and down-slanting palpebral fissures (62%) were most prevalent in MFS patients. CONCLUSION: Our data suggest there are quantitative differences in the facial morphology of patients with MFS when compared to a control population.

The small GTPases K-Ras, N-Ras, and H-Ras have distinct biochemical properties determined by allosteric effects.

H-Ras, K-Ras, and N-Ras are small GTPases that are important in the control of cell proliferation, differentiation, and survival, and their mutants occur frequently in human cancers. The G-domain, which catalyzes GTP hydrolysis and mediates downstream signaling, is 95% conserved between the Ras isoforms. Because of their very high sequence identity, biochemical studies done on H-Ras have been considered representative of all three Ras proteins. We show here that this is not a valid assumption. Using enzyme kinetic assays under identical conditions, we observed clear differences between the three isoforms in intrinsic catalysis of GTP by Ras in the absence and presence of the Ras-binding domain (RBD) of the c-Raf kinase protein (Raf-RBD). Given their identical active sites, isoform G-domain differences must be allosteric in origin, due to remote isoform-specific residues that affect conformational states. We present the crystal structure of N-Ras bound to a GTP analogue and interpret the kinetic data in terms of structural features specific for H-, K-, and N-Ras.

States' Methods for Capturing and Reporting Local Responses to Suspected Nonfatal Drug Overdoses.

This study examines the available data used to surveil state-level drug overdoses and characterizes them based on their timeliness, drug involvement, and specification of nonfatal outcomes.

Tyrosine phosphorylation of RAS by ABL allosterically enhances effector binding.

RAS proteins are signal transduction gatekeepers that mediate cell growth, survival, and differentiation through interactions with multiple effector proteins. The RAS effector RAS- and RAB-interacting protein 1 (RIN1) activates its own downstream effectors, the small GTPase RAB5 and the tyrosine kinase Abelson tyrosine-protein kinase (ABL), to modulate endocytosis and cytoskeleton remodeling. To identify ABL substrates downstream of RAS-to-RIN1 signaling, we examined human HEK293T cells overexpressing components of this pathway. Proteomic analysis revealed several novel phosphotyrosine peptides, including Harvey rat sarcoma oncogene (HRAS)-pTyr(137). Here we report that ABL phosphorylates tyrosine 137 of H-, K-, and NRAS. Increased RIN1 levels enhanced HRAS-Tyr(137) phosphorylation by nearly 5-fold, suggesting that RAS-stimulated RIN1 can drive ABL-mediated RAS modification in a feedback circuit. Tyr(137) is well conserved among RAS orthologs and is part of a transprotein H-bond network. Crystal structures of HRAS(Y137F) and HRAS(Y137E) revealed conformation changes radiating from the mutated residue. Although consistent with Tyr(137) participation in allosteric control of HRAS function, the mutations did not alter intrinsic GTP hydrolysis rates in vitro. HRAS-Tyr(137) phosphorylation enhanced HRAS signaling capacity in cells, however, as reflected by a 4-fold increase in the association of phosphorylated HRAS(G12V) with its effector protein RAF proto-oncogene serine/threonine protein kinase 1 (RAF1). These data suggest that RAS phosphorylation at Tyr(137) allosterically alters protein conformation and effector binding, providing a mechanism for effector-initiated modulation of RAS signaling.

Mesenchymal stromal cells for immunoregulation after liver transplantation: the scene in 2016.

PURPOSE OF REVIEW: The current review presents an update on the existing preclinical and human experience of mesenchymal stromal cell (MSC) therapies for post-transplant immunomodulation. RECENT FINDINGS: Although results from early clinical studies have demonstrated that the application of autologous and allogeneic MSC to be both safe and feasible in a solid organ transplantation setting, for example in liver, the efficacy of MSC immunotherapy demonstrated in preclinical models has yet to be replicated in human clinical trials. SUMMARY: Eagerly awaited results from the second generation of solid organ transplantation clinical trials, many of which are nearing completion, will perhaps establish the effectiveness of combining MSCs and low-dose pharmacological immunosuppression in promoting graft acceptance. At present, the question of whether infusional cell products based on MSCs will have a significant clinical impact in the field of liver transplantation remains open.

Caveats of mesenchymal stem cell therapy in solid organ transplantation.

In the past decade, therapeutic use of mesenchymal stem cells (MSCs) has increased dramatically. The weight of existing evidence supports that the short-term application of MSCs is safe and feasible; however, concerns remain over the possibility of unwanted long-term effects. One fundamental difference between MSCs and pharmacotherapy is that, once applied, the effects of cell products cannot be easily reversed. Therefore, a carefully considered decision process is indispensable before cell infusion. In addition to unwanted interactions of MSCs with the host immune system, there are concerns that MSCs may promote tumor progression or even give rise to cancer themselves. As animal models and first-in-man clinical studies have provided conflicting results, it is challenging to estimate the long-term risk of individual patients. In addition, most animal models, especially rodents, are ill-suited to adequately address questions over long-term side effects. Based on the available evidence, we address the potential pitfalls for the use of MSCs as a therapeutic agent to control alloimmune effects. The aim of this review was not to discourage investigators from clinical studies, but to raise awareness of the intrinsic risks of MSC therapy.

Rationale and prospects of mesenchymal stem cell therapy for liver transplantation.

PURPOSE OF REVIEW: Despite their potential to supplement the donor organ pool, expanded donor criteria grafts are associated with an elevated risk of graft failure and increased early mortality. Likewise, attempts to promote operational graft tolerance through conventional immunosuppressive therapy have demonstrated significant safety-related drawbacks. Because of their potent regenerative and immunomodulative potential, adjunct mesenchymal stem cell (MSC) therapy represents an innovative approach to both of these clinical problems. RECENT FINDINGS: Recent studies have begun to delineate the benefit and mechanisms of short-term therapy combining MSCs and low-dose immunosuppressive drugs in promoting graft acceptance and potentially regeneration. SUMMARY: The current review presents our rationale for the first-in-man clinical trial in liver transplantation utilizing a mesenchymal cell product (MultiStem, Athersys, Cleveland, Ohio, USA). The long-term objective of this program is to safely minimize the dose of complementary immunosuppressive drugs while achieving long-term allograft survival and operational tolerance. The use of adjunct cellular therapy as a means of reducing long-term pharmacotherapy would represent a major advancement in the field of liver transplantation.

State-level factors associated with implementation of prescription drug monitoring program integration and mandatory use policies, United States, 2009-2020.

BACKGROUND: Prescription drug monitoring programs (PDMPs) have been widely adopted as a tool to address the prescription opioid epidemic in the United States. PDMP integration and mandatory use policies are 2 approaches states have implemented to increase use of PDMPs by prescribers. While the effectiveness of these approaches is mixed, it is unclear what factors motivated states to implement them. This study examines whether opioid dispensing, adverse health outcomes, or other non-health-related factors motivated implementation of these PDMP approaches. METHODS: Time-to-event analysis was performed using lagged state-year covariates to reflect values from the year prior. Extended Cox regression estimated the association of states' rates of opioid dispensing, prescription opioid overdose deaths, and neonatal opioid withdrawal syndrome with implementation of PDMP integration and mandatory use policies from 2009 to 2020, controlling for demographic and economic factors, state government and political factors, and prior opioid policies. RESULTS: In our main model, prior opioid dispensing (HR 2.31, 95% CI 1.17, 4.57), neonatal opioid withdrawal syndrome hospitalizations (HR 1.55, 95% CI 1.09, 2.19), and number of prior opioid policies (HR 2.13, 95% CI 1.13, 4.00) were associated with mandatory use policies. Prior prescription opioid overdose deaths (HR 1.21, 95% CI 1.08, 1.35) were also associated with mandatory use policies in a model that did not include opioid dispensing or neonatal opioid withdrawal syndrome. No study variables were associated with implementation of PDMP integration. CONCLUSION: Understanding state-level factors associated with implementing PDMP approaches can provide insights into factors that motivate the adoption of future public health interventions.

Emergence and spread of Mycobacterium ulcerans at different geographic scales.

The classical lineage of Mycobacterium ulcerans is the most prevalent clonal group associated with Buruli ulcer in humans. Its reservoir is strongly associated with the environment. We analyzed together 1,045 isolates collected from 13 countries on two continents to define the evolutionary history and population dynamics of this lineage. We confirm that this lineage spread over 7,000 years from Australia to Africa with the emergence of outbreaks in distinct waves in the 18th and 19th centuries. In sharp contrast with its global spread over the last century, transmission chains are now mostly local, with little or no dissemination between endemic areas. This study provides new insights into the phylogeography and population dynamics of M. ulcerans, highlighting the importance of comparative genomic analyses to improve our understanding of pathogen transmission. IMPORTANCE: Mycobacterium ulcerans is an environmental mycobacterial pathogen that can cause Buruli ulcer, a severe cutaneous infection, mostly spread in Africa and Australia. We conducted a large genomic study of M. ulcerans, combining genomic and evolutionary approaches to decipher its evolutionary history and pattern of spread at different geographic scales. At the scale of villages in an endemic area of Benin, the circulating genotypes have been introduced in recent decades and are not randomly distributed along the river. On a global scale, M. ulcerans has been spreading for much longer, resulting in distinct and compartmentalized endemic foci across Africa and Australia.

Investigating the functional hierarchy of Bacillus megaterium PV361 spore germinant receptors.

Spores of Bacillus megaterium QM B1551 germinate rapidly when exposed to a number of single-trigger germinant compounds, including glucose, proline, leucine, and certain inorganic salts. However, spores of strain PV361, a plasmidless QM B1551 derivative that lacks the GerU germinant receptor (GR) responsible for mediating germination in response to single-trigger compounds, can germinate efficiently when incubated in nutritionally rich media, presumably via activation of additional germinant receptors. In this work, we have identified five chromosomally encoded GRs and attempted to characterize, by mutational analysis, germinant recognition profiles associated with the respective receptors in strain PV361. Of strains engineered with single GR insertion-deletions, only GerK-null spores displayed significant defective germination phenotypes when incubated in 5% (wt/vol) beef extract or plated on rich solid medium. Cumulative decreases in viability were observed in GerK-null spores that also lacked GerA or GerA2, indicating that these GRs, which exerted little effect on spore germination when disrupted individually, have a degree of functionality. Unexpectedly, an efficient germination response to combinations of germinants was restored in GerA(+) spores, which lack all other functional GRs, providing evidence for negative cooperativity between some GRs within the spore. Tetrazolium-based germinative assays conducted with purified spores indicated that these newly characterized B. megaterium GRs are cognate for a wide and chemically diverse range of germinant molecules, but unlike GerU, can only be induced to trigger germination when stimulated by at least two different germinants.

Integrating third-party apps with electronic health records to support COVID-19 response.

OBJECTIVES: To (1) track the integration of telehealth- and COVID-19-related apps with electronic health records (EHRs) over time, (2) identify the primary functionality of apps designed to support the COVID-19 response, and (3) examine whether apps available prior to the pandemic added new telehealth- or COVID-19-related functionalities during the pandemic. STUDY DESIGN: Data were collected from public EHR app galleries on a monthly basis from December 31, 2019, through June 1, 2021. METHODS: Apps were identified as relating to COVID-19 or telehealth using text analysis of the app marketing materials. Descriptive analyses were conducted to characterize telehealth- and COVID-19-related apps discovered through the app galleries, identify their primary functionality, and examine whether any apps added new telehealth- or COVID-19-related functionalities during the pandemic. RESULTS: The number of COVID-19-related apps increased from 0 in March 2020 to 19 a month later and continued to grow to 62 as of June 2021. The number of telehealth-related apps more than doubled from prepandemic levels (n = 41) to a total of 87 apps by June 2021. These apps were 2 times more likely to contain specialized capabilities used to support COVID-19 response efforts, such as secure messaging, vaccine administration, and laboratory testing, compared with all apps listed in the EHR app galleries. CONCLUSIONS: These findings demonstrate the potential of integrating third-party apps into EHRs to expand the range of tools that health care providers can use to diagnose, treat, and communicate with patients.

Disparities in patient portal access and the role of providers in encouraging access and use.

OBJECTIVE: The aim of this study was to identify racial and ethnic disparities in patient portal offers, access, and use and to examine the role of providers in facilitating access to electronic health information (EHI) by offering patient portals and encouraging their use. MATERIALS AND METHODS: Using nationally representative survey data from 2019 and 2020 (N = 8028), we examined disparities in patients being offered access to a portal by their provider and differences in subsequent access and use. Using multivariable models, we estimated the effect of race and ethnicity on the likelihood of being offered, accessing or using a portal. Among those offered, we examined the relationship between provider encouragement and portal access; and for those who did not access their portal, we explored reasons for nonuse. RESULTS: Black and Hispanic individuals were offered and accessed patient portals at significantly lower rates than White individuals. Compared to Whites, Black and Hispanic individuals were 5.2 percentage-points less likely to be offered a portal (P < .05) and, among those offered, 7.9 percentage-points less likely to access their portal (P < .05). Black and Hispanic individuals who were offered and accessed a portal were 12 percentage-points more likely than Whites to use it to download or transmit information (P < .01). Individuals who were offered a portal and encouraged to use it were 21 percentage-points more likely to access it. DISCUSSION: Differences in patient portal access and use are likely driven by disparities in which groups of patients reported being offered a portal. CONCLUSIONS: Providers play an important role in increasing access to EHI by facilitating access to patient portals.

All Roads Lead to Rome: YAP/TAZ Activity Influences Efficacy of KRASG12C Inhibitors.

The development of direct inhibitors of KRASG12C represents a monumental step forward in the field of oncology. Nevertheless, there is considerable opportunity to enhance response rates to KRASG12C inhibitors. In this issue of Cancer Research, three investigative teams explore the modulation of KRASG12C inhibitor activity in lung, colorectal, and pancreatic cancers using CRISPR-based knockout screens. While each group identified and validated a variety of genes and pathways conferring resistance to KRASG12C inhibition, all three groups converged upon activation of YAP/TAZ as a common means of resistance. While coinhibition of KRASG12C and YAP/TAZ did not cause complete tumor regression in xenograft models, combining YAP/TAZ inhibition was capable of significantly extending the response of tumors to KRASG12C inhibition. See related articles by Mukhopadhyay et al., p. 4095, Edwards et al., p. 4112, and Prahallad et al., p. 4130.

Allosteric site variants affect GTP hydrolysis on Ras.

RAS GTPases are proto-oncoproteins that regulate cell growth, proliferation, and differentiation in response to extracellular signals. The signaling functions of RAS, and other small GTPases, are dependent on their ability to cycle between GDP-bound and GTP-bound states. Structural analyses suggest that GTP hydrolysis catalyzed by HRAS can be regulated by an allosteric site located between helices 3, 4, and loop 7. Here we explore the relationship between intrinsic GTP hydrolysis on HRAS and the position of helix 3 and loop 7 through manipulation of the allosteric site, showing that the two sites are functionally connected. We generated several hydrophobic mutations in the allosteric site of HRAS to promote shifts in helix 3 relative to helix 4. By combining crystallography and enzymology to study these mutants, we show that closure of the allosteric site correlates with increased hydrolysis of GTP on HRAS in solution. Interestingly, binding to the RAS binding domain of RAF kinase (RAF-RBD) inhibits GTP hydrolysis in the mutants. This behavior may be representative of a cluster of mutations found in human tumors, which potentially cooperate with RAF complex formation to stabilize the GTP-bound state of RAS.

Allosteric Regulation of Switch-II Domain Controls KRAS Oncogenicity.

RAS proteins are GTPases that regulate a wide range of cellular processes. RAS activity is dependent on its nucleotide-binding status, which is modulated by guanine nucleotide exchange factors (GEF) and GTPase-activating proteins (GAP). KRAS can be acetylated at lysine 104 (K104), and an acetylation-mimetic mutation of K104 to glutamine (K104Q) attenuates the in vitro-transforming capacity of oncogenic KRAS by interrupting GEF-induced nucleotide exchange. To assess the effect of this mutation in vivo, we used CRISPR-Cas9 to generate mouse models carrying the K104Q point mutation in wild-type and conditional KrasLSL-G12D alleles. Homozygous animals for K104Q were viable, fertile, and arose at the expected Mendelian frequency, indicating that K104Q is not a complete loss-of-function mutation. Consistent with our previous findings from in vitro studies, however, the oncogenic activity of KRASG12D was significantly attenuated by mutation at K104. Biochemical and structural analysis indicated that the G12D and K104Q mutations cooperate to suppress GEF-mediated nucleotide exchange, explaining the preferential effect of K104Q on oncogenic KRAS. Furthermore, K104 functioned in an allosteric network with M72, R73, and G75 on the α2 helix of the switch-II region. Intriguingly, point mutation of glycine 75 to alanine (G75A) also showed a strong negative regulatory effect on KRASG12D. These data demonstrate that lysine at position 104 is critical for the full oncogenic activity of mutant KRAS and suggest that modulating the sites in its allosteric network may provide a unique therapeutic approach in cancers expressing mutant KRAS. SIGNIFICANCE: An allosteric network formed by interaction between lysine 104 and residues in the switch-II domain is required for KRAS oncogenicity, which could be exploited for developing inhibitors of the activated oncoprotein.

New EHR certification requirements and their association with duplicate tests and images.

BACKGROUND: Certified electronic health record (EHR) technology has been adopted by most hospitals and health care providers. In 2015, the Office of the National Coordinator for Health Information Technology (ONC) published new EHR certification requirements, known as the 2015 Edition. To date, no research has examined the impact of hospitals' adoption of the 2015 Edition on health care delivery. METHODS: We analyzed aggregated, longitudinal data drawn from a repository of deidentified health insurance claims collected by FAIR Health, the repository was estimated to represent about 75% of the privately insured in the United States. These data were linked with the American Hospital Association (AHA) Information Technology Supplement Survey to obtain hospitals' health information technology characteristics. A fixed effects specification was used to assess the incidence of duplicate testing and imaging in both inpatient and outpatient settings before and after the hospitals' adoption of the 2015 Edition. RESULTS: Hospitals with the 2015 Edition were less likely to perform duplicate imaging for inpatients by 5 percentage points (or 50% from baseline). Hospitals that adopted the 2015 Edition and actively engaged in interoperable data exchange were even less likely to perform duplicate lab tests. CONCLUSIONS: Adoption of the 2015 Edition certified EHR was negatively associated with the incidence of lab and imaging test duplication in both the outpatient and inpatient settings. However, the results were not robust across specifications. Given that multiple factors influence care delivery decisions, improvements in certification standards alone are unlikely to eliminate unneeded duplicate lab and imaging tests.

Classification of KRAS-Activating Mutations and the Implications for Therapeutic Intervention.

Members of the family of RAS proto-oncogenes, discovered just over 40 years ago, were among the first cancer-initiating genes to be discovered. Of the three RAS family members, KRAS is the most frequently mutated in human cancers. Despite intensive biological and biochemical study of RAS proteins over the past four decades, we are only now starting to devise therapeutic strategies to target their oncogenic properties. Here, we highlight the distinct biochemical properties of common and rare KRAS alleles, enabling their classification into functional subtypes. We also discuss the implications of this functional classification for potential therapeutic avenues targeting mutant subtypes. SIGNIFICANCE: Efforts in the recent past to inhibit KRAS oncogenicity have focused on kinases that function in downstream signal transduction cascades, although preclinical successes have not translated to patients with KRAS-mutant cancer. Recently, clinically effective covalent inhibitors of KRASG12C have been developed, establishing two principles that form a foundation for future efforts. First, KRAS is druggable. Second, each mutant form of KRAS is likely to have properties that make it uniquely druggable.