Structures of ABCB10, a human ATP-binding cassette transporter in apo- and nucleotide-bound states

ABCB10 is one of the three ATP-binding cassette (ABC) transporters found in the inner membrane of mitochondria. In mammals ABCB10 is essential for erythropoiesis, and for protection of mitochondria against oxidative stress. ABCB10 is therefore a potential therapeutic target for diseases in which increased mitochondrial reactive oxygen species production and oxidative stress play a major role. The crystal structure of apo-ABCB10 shows a classic exporter fold ABC transporter structure, in an open-inwards conformation, ready to bind the substrate or nucleotide from the inner mitochondrial matrix or membrane. Unexpectedly, however, ABCB10 adopts an open-inwards conformation when complexed with nonhydrolysable ATP analogs, in contrast to other transporter structures which adopt an open-outwards conformation in complex with ATP. The three complexes of ABCB10/ATP analogs reported here showed varying degrees of opening of the transport substrate binding site, indicating that in this conformation there is some flexibility between the two halves of the protein. These structures suggest that the observed plasticity, together with a portal between two helices in the transmembrane region of ABCB10, assist transport substrate entry into the substrate binding cavity. These structures indicate that ABC transporters may exist in an open-inwards conformation when nucleotide is bound. We discuss ways in which this observation can be aligned with the current views on mechanisms of ABC transporters.     

Cool and menthol receptor TRPM8 in human urinary bladder disorders and clinical correlations

Background

Macrophage migration inhibitory factor (MIF) is released into the intraluminal fluid during bladder inflammation in the rat complexed to α1-inhibitor-3 (A1-I3; a rodent proteinase inhibitor in the α-macroglobulin family). The location of A1-I3 in the bladder had not been investigated. Therefore, we examined the location of A1-I3 and MIF/A1-I3 complexes in the bladder and changes due to experimental inflammation.

Methods

Anesthetized male rats had bladders removed with no treatment (intact) or were injected with Substance P (SP; s.c.; saline vehicle). After one hour intraluminal fluid was removed, bladder was excised and MIF and A1-I3 levels were determined using ELISA and/or western-blotting. MIF co-immunoprecipitation determined MIF/A1-I3 complexes in the bladder. Bladder sections were immunostained for A1-I3 and MIF/A1-I3.

Results

A1-I3 immunostaining was observed in interstitial spaces throughout the bladder (including submucosa) but not urothelium in intact and saline-treated rats. RT-PCR showed that the bladder does not synthesize A1-I3, therefore, A1-I3 in the interstitial space of the bladder must be plasma derived. In SP-treated rats, A1-I3 in the bladder increased and A1-I3 was observed traversing through the urothelium. Umbrella cells that do not show MIF and/or A1-I3 immunostaining in intact or saline-treated rats, showed co-localization of MIF and A1-I3 after SP-treatment. Western blotting demonstrated that in the bladder MIF formed non-covalent interactions and also binds covalently to A1-I3 to form high molecular weight MIF/A1-I3 complexes (170, 130 and 75-kDa, respectively, verified by co-immunoprecipitation). SP-induced inflammation selectively reduced 170-kDa MIF/A1-I3 in the bladder while increasing 170 and 130-kDa MIF/A1-I3 in the intraluminal fluid.

Conclusion

A1-I3 and MIF/A1-I3 complexes are resident in bladder interstitium. During SP-induced inflammation, MIF/A1-I3 complexes are released from the bladder into the lumen. Binding of MIF/A1-I3 complexes to urothelial cells during inflammation suggests these complexes participate in the inflammatory reaction through activation of receptors for MIF and/or for A1-I3.     

Injuries of the heart and great vessels due to pins and needles

Three instances of cardiac injury from needles in two adults are described. Trauma was accidental in one and due to suicidal attempts in the other two. The objects were removed. There are 157 published accounts of wounding of the heart and/or great vessels by pins and needles. The victims have ranged from infants to the elderly. Causative agencies were accidents, suicide, and homicide. A few were discovered at necropsy in presumably asymptomatic persons. Six of the accidental injuries were iatrogenic. The objects reached the heart or great vessels from transthoracic insertion, ingestion, embolization, aspiration, or transabdominal penetration. The overall mortality incidence was about 50%. Acute cardiac tamponade was the dominant cause of death. Almost all individuals survived who were operated upon and from whom the object was removed. The right ventricle was hurt most often, but no region of the heart or of the great vessels was spared. Occasionally multiple parts were affected. The primary damage occurred principally while the foreign body was extracardiac and relatively immobilized, from repetitive scratching or puncturing of the beating heart. Chest pain and unfolding patterns of tamponade were inconsistent in onset, severity, and duration. Death ensuing days or weeks after the initial injury was frequent. Progressive haemopericardium in some cases was due to or aggravated by laceration of a structure from within outward. Late complications—several fatal—were consequent upon inflammation, sepsis or thromboembolism. It is urged that all foreign bodies in the heart or great vessels be retrieved, even if seemingly innocuous clinically.     

Pharmacological FMRI in the development of new analgesic compounds

Chronic pain is a major problem for the individual and for society. Despite a range of drugs being available to treat chronic pain, only inadequate pain relief can be achieved for many patients. There is therefore a need for the development of new analgesic compounds. The assessment of pain depends to date entirely on the subjective report of the patient, in contrast to many other clinical conditions where biomarkers that help determine the severity and stage of the disease enable the physician to monitor the course of the disease and treatment effects longitudinally. In this article, we illustrate that magnetic resonance-based imaging techniques have the potential to provide sensitive and specific biomarkers of the pain experience, as well as clarifying disease mechanisms. Functional magnetic resonance imaging (FMRI) is particularly suited to investigating the effects of pharmacological agents on pain processing within the human central nervous system. Combination of FMRI and drug administration is termed pharmacological FMRI (phFMRI). In addition to outlining several methodological considerations that have to be taken into account when performing phFMRI, we discuss phFMRI studies that have already used this technique to study the effects of analgesic compounds. These studies provide promising data for the use of phFMRI as sensitive tool in assessing a potential drug effect. Such pharmacodynamic readouts obtained early in the process of drug development would not only save the pharmaceutical industry substantial amounts of money, but would also avoid the unnecessary exposure of patients to molecules with limited or no therapeutic value. We are therefore optimistic that phFMRI will be used as a tool with high sensitivity and specificity for evaluating analgesic agents in early drug development and clinical studies.     

Unrealistic pessimism about risk of coronary heart disease and stroke in patients with type 2 diabetes

OBJECTIVE: We examined the accuracy of type 2 diabetes (T2D) patients' risk estimates of developing coronary heart disease (CHD)/having a stroke as a consequence of diabetes and their mood about these risks. METHODS: Patients reported their perceived risks of developing CHD/having a stroke and rated their mood about these risks using a self-report measure. Using an objective risk calculator, they were then told their actual risk of CHD and stroke and their mood was re-assessed. RESULTS: Patients' estimates of their risk of CHD/stroke were grossly inflated. A negative relationship between disease risk and mood was also seen where higher risk of actual and perceived CHD/stroke was related to worse mood. A positive relationship between mood and extent of perceptual error was further observed; the more inaccurate patients' perceptions of CHD/stroke risk were, the better their mood. Mood improved after patients were given accurate risk information. CONCLUSION: T2D patients are unrealistically pessimistic about their risk of developing CHD/stroke. These risks and the extent of perceptual risk error are associated with mood, which improves upon providing patients with accurate risk information about CHD/stroke. PRACTICE IMPLICATIONS: These results have implications for the routine communication of risk to T2D patients.