Development of an α-Klotho Recognizing High-Affinity Peptide Probe from In-Solution Enrichment

The kidney, parathyroid gland, and choroid plexus express the aging-related transmembrane protein α-Klotho, a coreceptor of the fibroblast growth factor 23 (FGF23) receptor complex. Reduced α-Klotho levels are correlated with chronic kidney disease and other age-related diseases, wherein they are released from membranes into circulation. Klotho's potential physiological action as a hormone is of current scientific interest. Part of the challenges associated with advancing these studies, however, has been the long-standing difficulty in detecting soluble α-Klotho in biofluids. Here, we describe the discovery of peptides that recognize α-Klotho with high affinity and selectivity by applying in-solution size-exclusion-based affinity selection-mass spectrometry (AS-MS). After two rounds of AS-MS and subsequent N-terminal modifications, the peptides improved their binding affinity to α-Klotho by approximately 2300-fold compared to the reported starting peptide Pep-10, previously designed based on the C-terminal region of FGF23. The lead peptide binders were shown to enrich α-Klotho from cell lysates and to label α-Klotho in kidney cells. Our results further support the utility of in-solution, label-free AS-MS protocols to discover peptide-based binders to target proteins of interest with high affinity and selectivity, resulting in functional probes for biological studies.

Structure of the p53 degradation complex from HPV16

Human papillomavirus (HPV) is a significant contributor to the global cancer burden, and its carcinogenic activity is facilitated in part by the HPV early protein 6 (E6), which interacts with the E3-ligase E6AP, also known as UBE3A, to promote degradation of the tumor suppressor, p53. In this study, we present a single-particle cryoEM structure of the full-length E6AP protein in complex with HPV16 E6 (16E6) and p53, determined at a resolution of ~3.3 Å. Our structure reveals extensive protein-protein interactions between 16E6 and E6AP, explaining their picomolar binding affinity. These findings shed light on the molecular basis of the ternary complex, which has been pursued as a potential therapeutic target for HPV-driven cervical, anal, and oropharyngeal cancers over the last two decades. Understanding the structural and mechanistic underpinnings of this complex is crucial for developing effective therapies to combat HPV-induced cancers. Our findings may help to explain why previous attempts to disrupt this complex have failed to generate therapeutic modalities and suggest that current strategies should be reevaluated.

Electrophile Scanning Reveals Reactivity Hotspots for the Design of Covalent Peptide Binders

Protein-protein interactions (PPIs) are intriguing targets in drug discovery and development. Peptides are well suited to target PPIs, which typically present with large surface areas lacking distinct features and deep binding pockets. To improve binding interactions with these topologies and advance the development of PPI-focused therapeutics, potential ligands can be equipped with electrophilic groups to enable binding through covalent mechanisms of action. We report a strategy termed electrophile scanning to identify reactivity hotspots in a known peptide ligand and demonstrate its application in a model PPI. Cysteine mutants of a known ligand are used to install protein-reactive modifiers via a palladium oxidative addition complex (Pd-OAC). Reactivity hotspots are revealed by cross-linking reactions with the target protein under physiological conditions. In a model PPI with the 9-mer peptide antigen VL9 and major histocompatibility complex (MHC) class I protein HLA-E, we identify two reactivity hotspots that afford up to 87% conversion to the protein-peptide conjugate within 4 h. The reactions are specific to the target protein in vitro and dependent on the peptide sequence. Moreover, the cross-linked peptide successfully inhibits molecular recognition of HLA-E by CD94-NKG2A possibly due to structural changes enacted at the PPI interface. The results illustrate the potential application of electrophile scanning as a tool for rapid discovery and development of covalent peptide binders.

Branched Multimeric Peptides as Affinity Reagents for the Detection of α-Klotho Protein

α-Klotho, an aging-related protein found in the kidney, parathyroid gland, and choroid plexus, acts as an essential co-receptor with the fibroblast growth factor 23 receptor complex to regulate serum phosphate and vitamin D levels. Decreased levels of α-Klotho are a hallmark of age-associated diseases. Detecting or labeling α-Klotho in biological milieu has long been a challenge, however, hampering the understanding of its role. Here, we developed branched peptides by single-shot parallel automated fast-flow synthesis that recognize α-Klotho with improved affinity relative to their monomeric versions. These peptides were further shown to selectively label Klotho for live imaging in kidney cells. Our results demonstrate that automated flow technology enables rapid synthesis of complex peptide architectures, showing promise for future detection of α-Klotho in physiological settings.

Survey of cancer cell anatomy in nonadhesive confinement reveals a role for filamin-A and fascin-1 in leader bleb-based migration

Cancer cells migrating in confined microenvironments exhibit plasticity of migration modes. Confinement of contractile cells in a nonadhesive environment drives “leader bleb–based migration” (LBBM), morphologically characterized by a long bleb that points in the direction of movement separated from a cell body by a contractile neck. Although cells undergoing LBBM have been visualized within tumors, the organization of organelles and actin regulatory proteins mediating LBBM is unknown. We analyzed the localization of fluorescent organelle-specific markers and actin-associated proteins in human melanoma and osteosarcoma cells undergoing LBBM. We found that organelles from the endolysosomal, secretory, and metabolic systems as well as the vimentin and microtubule cytoskeletons localized primarily in the cell body, with some endoplasmic reticulum, microtubules, and mitochondria extending into the leader bleb. Overexpression of fluorescently tagged actin regulatory proteins showed that actin assembly factors localized toward the leader bleb tip, contractility regulators and cross-linkers in the cell body cortex and neck, and cross-linkers additionally throughout the leader bleb. Quantitative analysis showed that excess filamin-A and fascin-1 increased migration speed and persistence, while their depletion by small interfering RNA indicates a requirement in promoting cortical tension and pressure to drive LBBM. This indicates a critical role of specific actin crosslinkers in LBBM.

Mechanisms of Motor-Independent Membrane Remodeling Driven by Dynamic Microtubules

Microtubule-dependent organization of membranous organelles occurs through motor-based pulling and by coupling microtubule dynamics to membrane remodeling. For example, tubules of endoplasmic reticulum (ER) can be extended by kinesin- and dynein-mediated transport and through the association with the tips of dynamic microtubules. The binding between ER and growing microtubule plus ends requires End Binding (EB) proteins and the transmembrane protein STIM1, which form a tip-attachment complex (TAC), but it is unknown whether these proteins are sufficient for membrane remodeling. Furthermore, EBs and their partners undergo rapid turnover at microtubule ends, and it is unclear how highly transient protein-protein interactions can induce load-bearing processive motion. Here, we reconstituted membrane tubulation in a minimal system with giant unilamellar vesicles, dynamic microtubules, an EB protein, and a membrane-bound protein that can interact with EBs and microtubules. We showed that these components are sufficient to drive membrane remodeling by three mechanisms: membrane tubulation induced by growing microtubule ends, motor-independent membrane sliding along microtubule shafts, and membrane pulling by shrinking microtubules. Experiments and modeling demonstrated that the first two mechanisms can be explained by adhesion-driven biased membrane spreading on microtubules. Optical trapping revealed that growing and shrinking microtubule ends can exert forces of ∼0.5 and ∼5 pN, respectively, through attached proteins. Rapidly exchanging molecules that connect membranes to dynamic microtubules can thus bear a sufficient load to induce membrane deformation and motility. Furthermore, combining TAC components and a membrane-attached kinesin in the same in vitro assays demonstrated that they can cooperate in promoting membrane tubule extension.

The erosion of the beaches on the coast of Alicante: Study of the mechanisms of weathering by accelerated laboratory tests

One of the main problems that coasts around the world present, is the regression and erosion of beaches. However, the factors involved in these processes are unclear. In this study, the influence of sediment erosion on beach regression has been analysed. In order to do that, a three-step investigation has been carried out. Firstly, coastline variations of four Spanish beaches have been analysed. Secondly, a study on sediment position along the beach profile has been developed. Finally, the process that beach sediments undergo along the surf zone when they are hit by the incident waves has been simulated by an accelerated particle weathering test. Samples of sand and shells were subjected to this accelerated particle weathering test. Results were supplemented with those from carbonate content test, XRD, SEM and granulometric analysis. Results shows a cross-shore classification of sediments along the beach profile in which finer particles move beyond offshore limit. Besides, it was observed that sediment erosion process is divided into three sages: i) particles wear due to crashes ii) dissolution of the carbonate fraction, and iii) breakage and separation of mineral and carbonate parts of particles. All these processes lead to a reduction of particle size. The mechanism responsible of beach erosion would consist of multiples and continuous particle location exchanges along the beach profile as a consequence of grain-size decrease due to erosion.

The impacts of Segura River (Spain) channelization on the coastal seabed

Human actions over rivers and coasts have generated great changes along seaboard. In order to know future development of those changes, it is necessary to understand the development of the coast during the past. When there is a complex morphologic system as a result of the combination of natural elements with human construction elements, the study of the abovementioned changes requires a wider perspective than the one provided by traditional two-dimensional methods. Thus, the Geographic Information Systems (GIS) become a suitable tool for that kind of studies. In this work, GIS are used to understand changes in bathymetry, sediments properties and transport, as well as surface variations of plant species occurred in the Segura River mouth (Spain) within a period of 17 years due to the channelization of the river low course. The methodology followed here implies the integration of data coming from different sources and with different formats in a GIS, what allows for a spatial analysis. Results obtained show the grain-size spatial distribution for every period of time studied, as well as bathymetry changes and seabed morphology. It can be concluded that the construction works carried out in the riverbed have affected sediment grain-size in the area. Clays have nearly disappeared and consequently there is a descent of seabed level that affects plant species, such as Posidonia oceanica.

Actin-microtubule coordination at growing microtubule ends

To power dynamic processes in cells, the actin and microtubule cytoskeletons organize into complex structures. Although it is known that cytoskeletal coordination is vital for cell function, the mechanisms by which cross-linking proteins coordinate actin and microtubule activities remain poorly understood. In particular, it is unknown how the distinct mechanical properties of different actin architectures modulate the outcome of actin-microtubule interactions. To address this question, we engineered the protein TipAct, which links growing microtubule ends via end-binding proteins to actin filaments. We show that growing microtubules can be captured and guided by stiff actin bundles, leading to global actin-microtubule alignment. Conversely, growing microtubule ends can transport, stretch and bundle individual actin filaments, thereby globally defining actin filament organization. Our results provide a physical basis to understand actin-microtubule cross-talk, and reveal that a simple cross-linker can enable a mechanical feedback between actin and microtubule organization that is relevant to diverse biological contexts.

In vitro reconstitution of dynamic microtubules interacting with actin filament networks

Interactions between microtubules and actin filaments (F-actin) are essential for eukaryotic cell migration, polarization, growth, and division. Although the importance of these interactions has been long recognized, the inherent complexity of the cell interior hampers a detailed mechanistic study of how these two cytoskeletal systems influence each other. In this chapter, we show how in vitro reconstitution can be employed to study how actin filaments and dynamic microtubules affect each other's organization. While we focus here on the effect of steric interactions, these assays provide an ideal starting point to develop more complex studies through the addition of known F-actin-microtubule cross-linkers, or myosin II motors.

Cortical dynein controls microtubule dynamics to generate pulling forces that position microtubule asters

Dynein at the cortex contributes to microtubule-based positioning processes such as spindle positioning during embryonic cell division and centrosome positioning during fibroblast migration. To investigate how cortical dynein interacts with microtubule ends to generate force and how this functional association impacts positioning, we have reconstituted the 'cortical' interaction between dynein and dynamic microtubule ends in an in vitro system using microfabricated barriers. We show that barrier-attached dynein captures microtubule ends, inhibits growth, and triggers microtubule catastrophes, thereby controlling microtubule length. The subsequent interaction with shrinking microtubule ends generates pulling forces up to several pN. By combining experiments in microchambers with a theoretical description of aster mechanics, we show that dynein-mediated pulling forces lead to the reliable centering of microtubule asters in simple confining geometries. Our results demonstrate the intrinsic ability of cortical microtubule-dynein interactions to regulate microtubule dynamics and drive positioning processes in living cells.

[Prolonged muscle weakness associated with the administration of non-depolarizing neuromuscular blocking agents in critically ill patients]

Generalized muscle weakness is a common disorder in patients undergoing mechanical ventilation. The cause is unknown but is attributed to the administration of non-depolarizing neuromuscular blocking and other drugs, mainly steroids, or to the presence of sepsis or multiorgan failure. Specific clinical pictures (polyneuropathy, myopathy and prolonged muscle weakness) develop in function of the underlying cause, although etiological factors may sometimes interact. Differential diagnosis is carried out with the aid of electromyography and pathology of the peripheral muscle. Costs are high and prognosis is uncertain. Completeness of neuromuscular blockade must be monitored in these patients to guide the administration of drugs, to avoid overdoses, to maintain muscle activity and to detect a chain of reactions among concomitant medications or pathophysiologic changes.

Molecular staging of non-small cell lung cancer according to K-ras genotypes

We have previously demonstrated a strong association between K-ras gene mutations, as determined by PCR followed by allele-specific oligonucleotide hybridization (ASO-h), and survival in non-small cell lung cancer patients. The purpose of this study was to determine the relationship between tumor aggressiveness and specific-type K-ras point mutations in non-small cell lung cancer. We developed procedures to examine the status of the K-ras gene by ASO-h and by single-strand conformation polymorphism assay of DNA obtained from formalin-fixed paraffin-embedded tumors. K-ras point mutations at codons 12 and 61 were assessed in 275 consecutively treated stage I-IV non-small cell lung cancers. Among patients with stage I disease, median survival time was 41.5 months in those whose tumors had no evidence of K-ras mutations and 27 months in those with K-ras 12 mutations; among patients with stage IIIA disease, median survival time was 7 months in those with K-ras codon 12 aspartic and serine mutations and 15 months for those with other K-ras mutations (P = 0.01). In a multivariate analysis, specific-type K-ras codon 12 point mutation remained a strong predictive factor (hazard ratio for death, 2.06; 95% confidence interval, 1.11-3.81; P = 0.02) after adjustment for other evaluated factors, including TNM stage and histology. Thus, we concluded that in patients with non-small cell lung cancer, specific K-ras 12 point mutations detected by DNA amplification and either ASO-h or single-strand conformation polymorphism methods predicted a significantly increased risk of recurrence and death, independently of stage and histology.

[Acute pancreatitis in patients infected with the human immunodeficiency virus]

This study was designed to define the etiological spectrum of acute pancreatitis in patients infected with HIV in our environment and to evaluate the relevance of cytomegalovirus as etiological agent. A retrospective analysis was first made of clinical, analytical, radiological and pathological findings of patients infected with HIV clinically diagnosed of acute pancreatitis (period 1984-1993). Then, clinical records of patients with necropsy proven CMV pancreatic involvement were retrospectively analyzed (period 1985-1992) to evaluate whether they had been diagnosed of acute pancreatitis when alive. Nine cases were diagnosed of acute pancreatitis. A presumptive etiology (didanosine) was considered in seven cases and idiopathic in two. Five patients died, two from causes directly related to acute pancreatitis. Necropsy was performed in two cases. Mortality was associated with the development of renal insufficiency or the appearance of three or more complications (p = 0.039). With regard to the second phase of the study CMV pancreatic involvement was demonstrated in 4 necropsies out of a total of 22 with evidence of CMV infection in one or more organs. None of these patients was diagnosed of acute pancreatitis when alive. Acute pancreatitis is an uncommon entity in patients infected with HIV. Presumptively, it could be attributed to didanosine therapy in most of our cases. The mortality rate was high, particularly when renal failure developed. In no case was CMV involved as etiologic agent when the patient was alive, although necropsy showed that pancreas can be subclinically involved in the context of a CMV disseminated infection.

[An evaluation of the infant program at a health center]

OBJECTIVE

Infant programme evaluation in our health centre.

DESIGN

Descriptive study, with random sample. SITE. Torrero-La Paz Health Centre in Zaragoza.

PATIENTS AND OTHER PARTICIPANTS

Fifty medical records of all the 275 infants younger than two years old included in the "Infant Programme".

MAIN MEASUREMENTS AND RESULTS

Some criteria were studied with its standards previously accented by the team. The obtained results were compared with the standards. The programme coverage was 70%, with 10% of loss. There were some criteria that indicated a good accomplishment of the programme, such as vaccination (87.2%), Hischberg test (87%), testicle examination (96.5%, preventive fluorine administration (92.5%). Others got lower results: dry spot screening (76%), maternal lactation advise (70%), maternal/mixed lactation at the third month (36%). The pathology detected in programmed check-ups was principally urologic disorders.

CONCLUSIONS

Poor structure for the programme performance in despite of the fact there is a good follow-up of the programme activities. It would be necessary to insist on the maternal lactation advise and lactation at the third month.

Glucose: a more powerful modulator of fructose 2,6-bisphosphate levels than insulin in human hepatocytes

This study provides the first experimental evidence of the short-term control of fructose 2,6-bisphosphate (Fru(2,6)P2) levels in adult human hepatocytes. (1) In hepatocytes whose metabolic status resembles the fed state (glycogen-rich), exposure to glucagon (10(-8) M) caused a drastic decrease in the levels of this effector and a significant fall in lactate production rate. Adrenaline, isoprenaline (a beta-adrenergic agonist) and lactate exerted a similar action decreasing Fru(2,6)P2 concentration. (2) In glucagon pre-treated, glycogen- and Fru(2,6)P2-depleted cells (a situation that mimics the fasted state), Fru(2,6)P2 re-synthesis was strictly dependent on glucose availability. (3) Insulin did not seem to exert a direct action on the control of Fru(2,6)P2 in human hepatocytes. The hormone--which failed to enhance Fru(2,6)P2 in glucose-starved cells--did not further increase Fru(2,6)P2 content nor its time-course evolution as compared to hepatocytes incubated with glucose alone. (4) Lactate caused a significant delay in the glucose-induced increase in Fru(2,6)P2 content that could not be prevented by insulin. (5) Data indicate that in human hepatocytes glucose is a more powerful modulator of Fru(2,6)P2 than insulin, and that variations in blood lactate concentration may also play a role in the control of hepatic Fru(2,6)P2 levels during the fasted-to-fed transition in humans.