Discovery of allosteric regulators with clinical potential to stabilize alpha-L-iduronidase in mucopolysaccharidosis type I.

Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal disease caused by lowered activity of the enzyme alpha-L-iduronidase (IDUA). Current therapeutic options show limited efficacy and do not treat some important aspects of the disease. Therefore, it may be advantageous to identify strategies that could improve the efficacy of existing treatments. Pharmacological chaperones are small molecules that protect proteins from degradation, and their use in combination with enzyme replacement therapy (ERT) has been proposed as an alternative therapeutic strategy. Using the SEE-Tx® proprietary computational drug discovery platform, a new allosteric ligand binding cavity in IDUA was identified distal from the active site. Virtual high-throughput screening of approximately 5 million compounds using the SEE-Tx® docking platform identified a subset of small molecules that bound to the druggable cavity and functioned as novel allosteric chaperones of IDUA. Experimental validation by differential scanning fluorimetry showed an overall hit rate of 11.4%. Biophysical studies showed that one exemplary hit molecule GT-01803 bound to (Kd = 22 µM) and stabilized recombinant human IDUA (rhIDUA) in a dose-dependent manner. Co-administration of rhIDUA and GT-01803 increased IDUA activity in patient-derived fibroblasts. Preliminary in vivo studies have shown that GT-01803 improved the pharmacokinetic (PK) profile of rhIDUA, increasing plasma levels in a dose-dependent manner. Furthermore, GT-01803 also increased IDUA enzymatic activity in bone marrow tissue, which benefits least from standard ERT. Oral bioavailability of GT-01803 was found to be good (50%). Overall, the discovery and validation of a novel allosteric chaperone for rhIDUA presents a promising strategy to enhance the efficacy of existing treatments for MPS I. The compound's ability to increase rhIDUA activity in patient-derived fibroblasts and its good oral bioavailability underscore its potential as a potent adjunct to ERT, particularly for addressing aspects of the disease less responsive to standard treatment.

Anterolateral Thigh Free Flap Donor-Site Morbidity: A Retrospective Cohort Study.

The ability to achieve a good functional outcome, quality of life, and patient satisfaction related to the donor site of free flaps is an important factor in flap selection. One of the main advantages of an anterolateral thigh (ALT) free flap is its minimal donor-site morbidity. We conducted a study to analyze healing of ALT flap donor sites based on the type of closure. A total of 65 patients were included in the study. We divided the participants into two cohorts (i.e., primary closure [n = 51] and skin grafting [n = 14]). There were no statistically significant differences between the two cohorts relative to age, gender, or risk factors for wound healing (e.g., tobacco use, obesity, diabetes mellitus, and cardiovascular disease). We found there was a statistically significant difference (p < .05) between the mean donor-site wound healing time in the primary closure group (n = 51; 22.41 days [±9.94]) compared with the skin grafting group (n = 14; 54.57 days [±21.59]). To reduce wound healing time, improve cosmetic results, and increase functional outcomes in patients undergoing ALT free flap, we recommend using primary closure for the donor sites and avoiding skin grafting whenever possible.

Vram flap transposition in pelviperineal reconstruction. A technical note.

The vertical rectus abdominis myocutaneous flap is a workhorse flap for perineal reconstruction after pelvic exenteration with low rate of complications. When flap viability is compromised, it is principally due to an incorrect inset or inadequate postoperative care. The aim of this article is to specify the technical details that must be taken into account during VRAM flap transposition inside the pelvis. Flap rotation will be completely different depending on two key factors: the resultant perineal defect after tumor resection and whether the patient is in the supine or prone position during the surgery. We expose an algorithmic approach to have in mind at the moment of the flap inset, step by step, in order not to compromise the vascular pedicle. In anterior perineal defects, we propose to rotate the flap 270º in the sagittal plane. In such manner, the cranial part of the flap covers the most anterior part of the defect, optimizing the arc of rotation of the flap. In posterior perineal defects, rotating the flap 180º in the coronal plane avoids tension on the pedicle. As a result, the cranial part of the flap covers the most posterior part of the defect. In our experience, these technical notes aid to guarantee the viability of the flap when performing perineal reconstructions, preventing from torsion or tension on the epigastric vessels during its transposition inside the pelvis.

Using Free Arterialized Venous Flaps for Reconstructing Hand Defects.

Hand and digit soft tissue defects are quite common and frequently require specialized reconstruction. When local flaps cannot be used to reconstruct a soft tissue defect, free flaps must be utilized. To overcome tissue volume and discrepancies in vessel diameter, arterialized venous free flaps from the forearm may provide an acceptable alternative. When using arterialized venous free flaps, surgeons should implement shunt restriction procedures to enhance flap viability.

Soft-Tissue Sarcoma as a Potential Differential Diagnosis of an Exophytic Soft-Tissue Mass: A Case Report.

The detection of a soft-tissue mass requires a detailed and conscientious examination to make a definitive diagnosis and propose appropriate treatment strategies. Benign mesenchymal tumors occur more frequently than malignant tumors. However, because of their aggressive growth and poor prognosis, sarcomas must always be considered as a potential differential diagnosis. To make a formal diagnosis and plan appropriate surgical treatment, the surgeon should obtain cross-sectional imaging studies and biopsies.

Omental free flap for surgical treatment of chronic osteomyelitis of lower limb: A technical note.

Soft tissue reconstruction of chronic lower extremity wounds with bone infection entails an important challenge in reconstructive surgery. We report our experience using the omentum free flap to provide coverage in two patients suffering chronic osteomyelitis of the lower limbs. After extensive soft tissue and bone debridement, an omentum free flap was performed in both cases, providing dead space obliteration and soft tissue coverage in behalf of its large size and pliability. As a result, the chronic illness was eradicated in both patients, with satisfactory outcomes and infection resolution.

Atypical Presentation of a Marjolin Ulcer After a Burn: A Case Report.

The development of a nonhealing ulcer on a chronic wound or scar should raise suspicions of the plastic surgeon or nurse regarding the potential for malignant degeneration to a Marjolin ulcer. Occasionally, a Marjolin ulcer may present as exophytic granulation tissue within a scar. Most Marjolin ulcers are well-differentiated injuries; however, because of their aggressive nature and poor prognosis, to ensure surgical success, diagnosis of Marjolin ulcer should be confirmed and treatment initiated as soon as possible.

Correction: Photoswitchable dynasore analogs to control endocytosis with light.

[This corrects the article DOI: 10.1039/D0SC03820B.].

Use of Amniotic Membrane as a Biological Dressing for the Treatment of Torpid Venous Ulcers: A Case Report.

Chronic venous disease manifested as ulcers in the lower limb is a highly prevalent pathology in our population. Antiseptics and dressings designed to improve epithelialization are often used to cure the ulcer during outpatient therapy. Despite careful management, sometimes ulcers do not respond to treatment. In this report, we discuss the antiseptic and potentially immunomodulatory effects of the amniotic membrane as a biological dressing for the treatment of venous ulcers refractory to conventional therapy.

Covalent inactivation of Mycobacterium thermoresistibile inosine-5'-monophosphate dehydrogenase (IMPDH).

Inosine-5'-monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme involved in nucleotide biosynthesis. Because of its critical role in purine biosynthesis, IMPDH is a drug design target for immunosuppressive, anticancer, antiviral and antimicrobial chemotherapy. In this study, we use mass spectrometry and X-ray crystallography to show that the inhibitor 6-Cl-purine ribotide forms a covalent adduct with the Cys-341 residue of Mycobacterium thermoresistibile IMPDH.

A Light-Controlled Allosteric Modulator Unveils a Role for mGlu4 Receptors During Early Stages of Ischemia in the Rodent Cerebellar Cortex.

Metabotropic glutamate receptors (mGlus) are G Protein coupled-receptors that modulate synaptic transmission and plasticity in the central nervous system. Some act as autoreceptors to control neurotransmitter release at excitatory synapses and have become attractive targets for drug therapy to treat certain neurological disorders. However, the high degree of sequence conservation around the glutamate binding site makes the development of subtype-specific orthosteric ligands difficult to achieve. This problem can be circumvented by designing molecules that target specific less well conserved allosteric sites. One such allosteric drug, the photo-switchable compound OptoGluNAM4.1, has been recently employed to reversibly inhibit the activity of metabotropic glutamate 4 (mGlu4) receptors in cell cultures and in vivo. We studied OptoGluNAM4.1 as a negative modulator of neurotransmission in rodent cerebellar slices at the parallel fiber - Purkinje cell synapse. Our data show that OptoGluNAM4.1 antagonizes pharmacological activation of mGlu4 receptors in a fully reversible and photo-controllable manner. In addition, for the first time, this new allosteric modulator allowed us to demonstrate that, in brain slices from the rodent cerebellar cortex, mGlu4 receptors are endogenously activated in excitotoxic conditions, such as the early phases of simulated cerebellar ischemia, which is associated with elevated levels of extracellular glutamate. These findings support OptoGluNAM4.1 as a promising new tool for unraveling the role of mGlu4 receptors in the central nervous system in physio-pathological conditions.

Fragment-Based Approach to Targeting Inosine-5'-monophosphate Dehydrogenase (IMPDH) from Mycobacterium tuberculosis.

Tuberculosis (TB) remains a major cause of mortality worldwide, and improved treatments are needed to combat emergence of drug resistance. Inosine 5'-monophosphate dehydrogenase (IMPDH), a crucial enzyme required for de novo synthesis of guanine nucleotides, is an attractive TB drug target. Herein, we describe the identification of potent IMPDH inhibitors using fragment-based screening and structure-based design techniques. Screening of a fragment library for Mycobacterium thermoresistible ( Mth) IMPDH ΔCBS inhibitors identified a low affinity phenylimidazole derivative. X-ray crystallography of the Mth IMPDH ΔCBS-IMP-inhibitor complex revealed that two molecules of the fragment were bound in the NAD binding pocket of IMPDH. Linking the two molecules of the fragment afforded compounds with more than 1000-fold improvement in IMPDH affinity over the initial fragment hit.

Allosteric control of an asymmetric transduction in a G protein-coupled receptor heterodimer.

GPCRs play critical roles in cell communication. Although GPCRs can form heteromers, their role in signaling remains elusive. Here we used rat metabotropic glutamate (mGlu) receptors as prototypical dimers to study the functional interaction between each subunit. mGluRs can form both constitutive homo- and heterodimers. Whereas both mGlu2 and mGlu4 couple to G proteins, G protein activation is mediated by mGlu4 heptahelical domain (HD) exclusively in mGlu2-4 heterodimers. Such asymmetric transduction results from the action of both the dimeric extracellular domain, and an allosteric activation by the partially-activated non-functional mGlu2 HD. G proteins activation by mGlu2 HD occurs if either the mGlu2 HD is occupied by a positive allosteric modulator or if mGlu4 HD is inhibited by a negative modulator. These data revealed an oriented asymmetry in mGlu heterodimers that can be controlled with allosteric modulators. They provide new insight on the allosteric interaction between subunits in a GPCR dimer.

OptoGluNAM4.1, a Photoswitchable Allosteric Antagonist for Real-Time Control of mGlu4 Receptor Activity.

OptoGluNAM4.1, a negative allosteric modulator (NAM) of metabotropic glutamate receptor 4 (mGlu4) contains a reactive group that covalently binds to the receptor and a blue-light-activated, fast-relaxing azobenzene group that allows reversible receptor activity photocontrol in vitro and in vivo. OptoGluNAM4.1 induces light-dependent behavior in zebrafish and reverses the activity of the mGlu4 agonist LSP4-2022 in a mice model of chronic pain, defining a photopharmacological tool to better elucidate the physiological roles of the mGlu4 receptor in the nervous system.

Optical control of endogenous receptors and cellular excitability using targeted covalent photoswitches.

Light-regulated drugs allow remotely photoswitching biological activity and enable plausible therapies based on small molecules. However, only freely diffusible photochromic ligands have been shown to work directly in endogenous receptors and methods for covalent attachment depend on genetic manipulation. Here we introduce a chemical strategy to covalently conjugate and photoswitch the activity of endogenous proteins and demonstrate its application to the kainate receptor channel GluK1. The approach is based on photoswitchable ligands containing a short-lived, highly reactive anchoring group that is targeted at the protein of interest by ligand affinity. These targeted covalent photoswitches (TCPs) constitute a new class of light-regulated drugs and act as prosthetic molecules that photocontrol the activity of GluK1-expressing neurons, and restore photoresponses in degenerated retina. The modularity of TCPs enables the application to different ligands and opens the way to new therapeutic opportunities.

Galacto configured N-aminoaziridines: a new type of irreversible inhibitor of ß-galactosidases.

A new type of galactose mimetics has been synthesized following a straightforward synthetic approach based on cyclohexene olefin aziridination reactions directed by hydroxyl substituents. These enantiomerically pure galacto-configured N-aminoaziridines are potent irreversible inhibitors of Aspergillus oryzae and Escherichia coliß-galactosidases.