Structural analysis of P. falciparum KAHRP and PfEMP1 complexes with host erythrocyte spectrin suggests a model for cytoadherent knob protrusions.

Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) and Knob-associated Histidine-rich Protein (KAHRP) are directly linked to malaria pathology. PfEMP1 and KAHRP cluster on protrusions (knobs) on the P. falciparum-infected erythrocyte surface and enable pathogenic cytoadherence of infected erythrocytes to the host microvasculature, leading to restricted blood flow, oxygen deprivation and damage of tissues. Here we characterize the interactions of PfEMP1 and KAHRP with host erythrocyte spectrin using biophysical, structural and computational approaches. These interactions assist knob formation and, thus, promote cytoadherence. We show that the folded core of the PfEMP1 cytosolic domain interacts broadly with erythrocyte spectrin but shows weak, residue-specific preference for domain 17 of α spectrin, which is proximal to the erythrocyte cytoskeletal junction. In contrast, a protein sequence repeat region in KAHRP preferentially associates with domains 10-14 of ß spectrin, proximal to the spectrin-ankyrin complex. Structural models of PfEMP1 and KAHRP with spectrin combined with previous microscopy and protein interaction data suggest a model for knob architecture.

Elective Cardioversion in the Era of Novel Oral Anticoagulants - Does a Nurse Administered Verbal Questionnaire for Compliance Negate the Need for Routine Transoesophageal Echocardiography?

BACKGROUND: Anticoagulation prior to elective external direct current cardioversion (EDCCV) is mandatory. The inability to monitor compliance with novel oral anticoagulants (NOACs) raises a potential safety issue. We aimed to evaluate whether a structured, nurse-led assessment of compliance prior to EDCCV ensures safety without the need for routine transoesophageal echocardiography (TOE). METHODS: Data was prospectively collected on consecutive patients undergoing EDCCV during 2014-2015. All procedures were supervised by an electrophysiology clinical nurse consultant (EPCNC). Drug compliance was verbally assessed using a standardised questionnaire by the EPCNC. Novel oral anticoagulants compliance was required for a continuous period of 3 weeks prior to EDCCV; otherwise a TOE-guided EDDCV was performed. All patients had follow-up 30 days post-procedure. RESULTS: Three hundred and eleven cardioversions were performed on 256 patients in whom 154 (49.5%) were prescribed a NOAC (rivaroxaban (n=105; 68.2%), dabigatran (n=38; 24.7%), apixaban (n=11; 7.1%)). Median age was 63 years (24-94 yrs), mean CHADS2-Vasc score was 2.0±1.5 and 138 (89.6%) were outpatients. One hundred and twenty-nine (83.8%) EDCCV were for atrial fibrillation and 25 (16.2%) for atrial flutter. Sinus rhythm was achieved in 90.3% of cases. Fourteen patients (9%) assessed as non-compliant underwent TOE. 129 (83.8%) EDCCV were performed without prior TOE. No stroke or systemic embolism was identified in any patient treated with either warfarin or a NOAC. CONCLUSIONS: A standardised, verbal questionnaire can be administered to detect NOAC non-compliance in patients undergoing EDCCV. With appropriate compliance assessment a nurse-led EDCCV without routine TOE did not significantly compromise safety in this study group.

Caenorhabditis elegans centriolar protein SAS-6 forms a spiral that is consistent with imparting a ninefold symmetry.

Centrioles are evolutionary conserved organelles that give rise to cilia and flagella as well as centrosomes. Centrioles display a characteristic ninefold symmetry imposed by the spindle assembly abnormal protein 6 (SAS-6) family. SAS-6 from Chlamydomonas reinhardtii and Danio rerio was shown to form ninefold symmetric, ring-shaped oligomers in vitro that were similar to the cartwheels observed in vivo during early steps of centriole assembly in most species. Here, we report crystallographic and EM analyses showing that, instead, Caenorhabotis elegans SAS-6 self-assembles into a spiral arrangement. Remarkably, we find that this spiral arrangement is also consistent with ninefold symmetry, suggesting that two distinct SAS-6 oligomerization architectures can direct the same output symmetry. Sequence analysis suggests that SAS-6 spirals are restricted to specific nematodes. This oligomeric arrangement may provide a structural basis for the presence of a central tube instead of a cartwheel during centriole assembly in these species.

A Plasmodium falciparum PHIST protein binds the virulence factor PfEMP1 and comigrates to knobs on the host cell surface.

Uniquely among malaria parasites, Plasmodium falciparum-infected erythrocytes (iRBCs) develop membrane protrusions, known as knobs, where the parasite adhesion receptor P. falciparum erythrocyte membrane protein 1 (PfEMP1) clusters. Knob formation and the associated iRBC adherence to host endothelium are directly linked to the severity of malaria and are functional manifestations of protein export from the parasite to the iRBC. A family of exported proteins featuring Plasmodium helical interspersed subtelomeric (PHIST) domains has attracted attention, with members being implicated in host-parasite protein interactions and differentially regulated in severe disease and among parasite isolates. Here, we show that PHIST member PFE1605w binds the PfEMP1 intracellular segment directly with Kd = 5 ± 0.6 µM, comigrates with PfEMP1 during export, and locates in knobs. PHIST variants that do not locate in knobs (MAL8P1.4) or bind PfEMP1 30 times more weakly (PFI1780w) used as controls did not display the same pattern. We resolved the first crystallographic structure of a PHIST protein and derived a partial model of the PHIST-PfEMP1 interaction from nuclear magnetic resonance. We propose that PFE1605w reinforces the PfEMP1-cytoskeletal connection in knobs and discuss the possible role of PHIST proteins as interaction hubs in the parasite exportome.

Seven years experience of a nurse-led elective cardioversion service in a tertiary referral centre: an observational study.

BACKGROUND: Traditionally the provision of elective external direct current cardioversion (EDCCV) for patients with atrial arrhythmias has been doctor-led. Increasing demands on hospital beds and time pressures for doctors has driven the desire for an alternative approach. We established a nurse-led cardioversion service in 2006 and present our experience. METHODS: A prospective database of patients undergoing elective EDCCV between July 2006 and July 2013 was collected. Demographic data, arrhythmia, success and immediate complications of cardioversion were recorded. RESULTS: A total of 974 EDCCV were performed on 772 patients. The mean patient age was 62.7 years, 564 (73.1%) were male. In 530 patients (69.0%) AF was the primary arrhythmia, in 242 (31.0%) atrial flutter. All EDCCVs were performed in a high dependency unit. Sinus rhythm was obtained in 692 patients (89.6%). Of 640 outpatients, 629 (98.3%) were discharged on the same day of their procedure. Eleven patients (1.7%) required admission to hospital. No patients required urgent temporary transvenous or permanent pacing, and there were no deaths in association with this procedure. CONCLUSIONS: Nurse-led elective EDCCV is a safe and effective way of restoring sinus rhythm in patients with AF or atrial flutter, with additional benefits to resource provision.

Structural analysis of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) intracellular domain reveals a conserved interaction epitope.

Plasmodium falciparum-infected red blood cells adhere to endothelial cells, thereby obstructing the microvasculature. Erythrocyte adherence is directly associated with severe malaria and increased disease lethality, and it is mediated by the PfEMP1 family. PfEMP1 clustering in knob-like protrusions on the erythrocyte membrane is critical for cytoadherence, however the molecular mechanisms behind this system remain elusive. Here, we show that the intracellular domains of the PfEMP1 family (ATS) share a unique molecular architecture, which comprises a minimal folded core and extensive flexible elements. A conserved flexible segment at the ATS center is minimally restrained by the folded core. Yeast-two-hybrid data and a novel sequence analysis method suggest that this central segment contains a conserved protein interaction epitope. Interestingly, ATS in solution fails to bind the parasite knob-associated histidine-rich protein (KAHRP), an essential cytoadherence component. Instead, we demonstrate that ATS associates with PFI1780w, a member of the Plasmodium helical interspersed sub-telomeric (PHIST) family. PHIST domains are widespread in exported parasite proteins, however this is the first specific molecular function assigned to any variant of this family. We propose that PHIST domains facilitate protein interactions, and that the conserved ATS epitope may be targeted to disrupt the parasite cytoadherence system.

The clinimetric properties of performance-based gross motor tests used for children with developmental coordination disorder: a systematic review.

PURPOSE: Performance-based measures of gross motor skills are required for children with developmental coordination disorder to quantify motor ability and objectify change. Information related to psychometrics, clinical utility, feasibility, and client appropriateness and acceptability is needed so that clinicians and researchers are assured that they have chosen the most appropriate and robust tool. METHODS: This review identified performance-based measures of gross motor skills for this population, and the research evidence for their clinimetric properties through a systematic literature search. RESULTS: Seven measures met the inclusion criteria and were appraised for their clinimetric properties. The Movement Assessment Battery for Children and the Test for Gross Motor Development (second version) scored highest on appraisal. CONCLUSIONS: The 2 highest scoring measures are recommended in the first instance for clinicians wishing to evaluate gross motor performance in children with developmental coordination disorder. However, both measures require further testing to increase confidence in their validity for this population.

Structural variation in PWWP domains.

The PWWP domain is a ubiquitous eukaryotic protein module characterised by a region of sequence similarity of approximately 80 amino acids containing a highly conserved PWWP motif. It is frequently found in proteins associated with chromatin. We have determined the structure of a PWWP domain from the S. pombe protein SPBC215.07c using NMR spectroscopy. The structure is composed of a five stranded beta barrel followed by two alpha helices. Comparison to the recently reported structure of a homologous domain from the mammalian DNA methyltransferase Dnmt3b reveals substantial differences both in the C-terminal helical region and in the PWWP motif.

Structural analysis of the G-box domain of the microcephaly protein CPAP suggests a role in centriole architecture.

Centrioles are evolutionarily conserved eukaryotic organelles composed of a protein scaffold surrounded by sets of microtubules organized with a 9-fold radial symmetry. CPAP, a centriolar protein essential for microtubule recruitment, features a C-terminal domain of unknown structure, the G-box. A missense mutation in the G-box reduces affinity for the centriolar shuttling protein STIL and causes primary microcephaly. Here, we characterize the molecular architecture of CPAP and determine the G-box structure alone and in complex with a STIL fragment. The G-box comprises a single elongated ß sheet capable of forming supramolecular assemblies. Structural and biophysical studies highlight the conserved nature of the CPAP-STIL complex. We propose that CPAP acts as a horizontal "strut" that joins the centriolar scaffold with microtubules, whereas G-box domains form perpendicular connections.