Destabilization of the SHP2 and SHP1 protein tyrosine phosphatase domains by a non-conserved "backdoor" cysteine.

Protein tyrosine phosphatases (PTPs) are critical regulators of cellular signal transduction that catalyze the hydrolytic dephosphorylation of phosphotyrosine in substrate proteins. Among several conserved features in classical PTP domains are an active-site cysteine residue that is necessary for catalysis and a "backdoor" cysteine residue that can serve to protect the active-site cysteine from irreversible oxidation. Curiously, two biologically important phosphatases, Src homology domain-containing PTPs 2 and 1 (SHP2 and SHP1), each contain an additional backdoor cysteine residue at a position of the PTP domain that is occupied by proline in almost all other classical PTPs (position 333 in human SHP2 numbering). Here we show that the presence of cysteine 333 significantly destabilizes the fold of the PTP domains in the SHPs. We find that replacement of cysteine 333 with proline confers increased thermal stability on the SHP2 and SHP1 PTP domains, as measured by temperature-dependent activity assays and differential scanning fluorimetry. Conversely, we show that substantial destabilization of the PTP-domain fold is conferred by introduction of a non-natural cysteine residue in a non-SHP PTP that contains proline at the 333 position. It has previously been suggested that the extra backdoor cysteine of the SHP PTPs may work in tandem with the conserved backdoor cysteine to provide protection from irreversible oxidative enzyme inactivation. If so, our current results suggest that, during the course of mammalian evolution, the SHP proteins have developed extra protection from oxidation at the cost of the thermal instability that is conferred by the presence of their PTP domains' second backdoor cysteine.

Management of Muscle Spasms in Adult Patients with Cerebral Palsy.

As medical care advances, there is a growing number of adult patients with cerebral palsy. The spastic form is characterized by muscle hypertonicity, hyperreflexia, and spasticity, which are associated with worse quality of life, poor functionality, and pain. This literature review attempts to explore the existing treatments for spasticity in cerebral palsy to provide insight into potential treatments in the adult population. The types of treatments are broadly categorized into physical therapy, pharmacologic treatments, botulinum toxin, surgical treatments, and alternative options.

The Vitreous Ecosystem in Diabetic Retinopathy: Insight into the Patho-Mechanisms of Disease.

Diabetic retinopathy is one of the leading causes of blindness in the world with the incidence of disease ever-increasing worldwide. The vitreous humor represents an extensive and complex interactive arena for cytokines in the diabetic eye. In recent decades, there has been significant progress in understanding this environment and its implications in disease pathophysiology. In this review, we investigate the vitreous ecosystem in diabetic retinopathy at the molecular level. Areas of concentration include: the current level of knowledge of growth factors, cytokine and chemokine mediators, and lipid-derived metabolites in the vitreous. We discuss the molecular patho-mechanisms of diabetic retinopathy based upon current vitreous research.

The Allosteric Site on SHP2's Protein Tyrosine Phosphatase Domain is Targetable with Druglike Small Molecules.

Difficulties in developing active-site-directed protein tyrosine phosphatase (PTP) inhibitors have led to the perception that PTPs are "undruggable", highlighting the need for new means to target pharmaceutically important PTPs allosterically. Recently, we characterized an allosteric-inhibition site on the PTP domain of Src-homology-2-domain-containing PTP 2 (SHP2), a key anticancer drug target. The central feature of SHP2's allosteric site is a nonconserved cysteine residue (C333) that can potentially be labeled with electrophilic compounds for selective SHP2 inhibition. Here, we describe the first directed discovery effort for C333-targeted allosteric SHP2 inhibitors. By screening a previously reported library of reversible, covalent inhibitors, we identified a lead compound, which was modified to yield an irreversible inhibitor (12), that inhibits SHP2 allosterically and selectively through interaction with C333. These findings provide a novel paradigm for allosteric-inhibitor discovery on SHP2, one that may help to circumvent the challenges inherent in targeting SHP2's active site.

Optimized allosteric inhibition of engineered protein tyrosine phosphatases with an expanded palette of biarsenical small molecules.

Protein tyrosine phosphatases (PTPs), which catalyze the dephosphorylation of phosphotyrosine in protein substrates, are important cell-signaling regulators, as well as potential drug targets for a range of human diseases. Chemical tools for selectively targeting the activities of individual PTPs would help to elucidate PTP signaling roles and potentially expedite the validation of PTPs as therapeutic targets. We have recently reported a novel strategy for the design of non-natural allosteric-inhibition sites in PTPs, in which a tricysteine moiety is engineered within the PTP catalytic domain at a conserved location outside of the active site. Introduction of the tricysteine motif, which does not exist in any wild-type PTP, serves to sensitize target PTPs to inhibition by a biarsenical compound, providing a generalizable strategy for the generation of allosterically sensitized (as) PTPs. Here we show that the potency, selectivity, and kinetics of asPTP inhibition can be significantly improved by exploring the inhibitory action of a range of biarsenical compounds that differ in interarsenical distance, steric bulk, and electronic structure. By investigating the inhibitor sensitivities of five asPTPs from four different subfamilies, we have found that asPTP catalytic domains can be broadly divided into two groups: one that is most potently inhibited by biarsenical compounds with large interarsenical distances, such as AsCy3-EDT2, and one that is most potently inhibited by compounds with relatively small interarsenical distances, such as FlAsH-EDT2. Moreover, we show that a tetrachlorinated derivative of FlAsH-EDT2, Cl4FlAsH-EDT2, targets asPTPs significantly more potently than the parent compound, both in vitro and in asPTP-expressing cells. Our results show that biarsenicals with altered interarsenical distances and electronic properties are important tools for optimizing the control of asPTP activity and, more broadly, suggest that diversification of biarsenical libraries can serve to increase the efficacy of these compounds in targeted control of protein function.

Implementation of a quality improvement project on smoking cessation reduces smoking in a high risk trauma patient population.

BACKGROUND: Cigarette smoking causes about one of every five deaths in the U.S. each year. In 2013 the prevalence of smoking in our institution's trauma population was 26.7 %, well above the national adult average of 18.1 % according to the CDC website. As a quality improvement project we implemented a multimodality smoking cessation program in a high-risk trauma population. METHODS: All smokers with independent mental capacity admitted to our level I trauma center from 6/1/2014 until 3/31/2015 were counseled by a physician on the benefits of smoking cessation. Those who wished to quit smoking were given further counseling by a pulmonary rehabilitation nurse and offered nicotine replacement therapy (e.g. nicotine patch). A planned 30 day or later follow-up was performed to ascertain the primary endpoint of the total number of patients who quit smoking, with a secondary endpoint of reduction in the frequency of smoking, defined as at least a half pack per day reduction from their pre-intervention state. RESULTS: During the 9 month study period, 1066 trauma patients were admitted with 241 (22.6 %) identified as smokers. A total of 31 patients with a mean Injury Severity Score (ISS) of 14.2 (range 1-38), mean age of 47.6 (21-71) and mean years of smoking of 27.1 (2-55), wished to stop smoking. Seven of the 31 patients, (22.5 %, 95 % confidence interval [CI] of 10-41 %) achieved self-reported smoking cessation at or beyond 30 days post discharge. An additional eight patients (25.8 %, 95 % CI 12-45 %) reported significant reduction in smoking. CONCLUSIONS: Trauma patients represent a high risk smoking population. The implementation of a smoking cessation program led to a smoking cessation rate of 22.5 % and smoking reduction in 25.8 % of all identified smokers who participated in the program. This is a relatively simple, inexpensive intervention with potentially far reaching and beneficial long-term health implications. A larger, multi-center prospective study appears warranted. LEVEL OF EVIDENCE: Therapeutic Study, Level V evidence.