CapZ-lipid membrane interactions: a computer analysis

BACKGROUND: CapZ is a calcium-insensitive and lipid-dependent actin filament capping protein, the main function of which is to regulate the assembly of the actin cytoskeleton. CapZ is associated with membranes in cells and it is generally assumed that this interaction is mediated by polyphosphoinositides (PPI) particularly PIP(2), which has been characterized in vitro. RESULTS: We propose that non-PPI lipids also bind CapZ. Data from computer-aided sequence and structure analyses further suggest that CapZ could become partially buried in the lipid bilayer probably under mildly acidic conditions, in a manner that is not only dependent on the presence of PPIs. We show that lipid binding could involve a number of sites that are spread throughout the CapZ molecule i.e., alpha- and beta-subunits. However, a beta-subunit segment between residues 134–151 is most likely to be involved in interacting with and inserting into lipid membrane due to a slighly higher ratio of positively to negatively charged residues and also due to the presence of a small hydrophobic helix. CONCLUSION: CapZ may therefore play an essential role in providing a stable membrane anchor for actin filaments

The affinity of GXXXG motifs in transmembrane helix-helix interactions is modulated by long-range communication

Sequence motifs are responsible for ensuring the proper assembly of transmembrane (TM) helices in the lipid bilayer. To understand the mechanism by which the affinity of a common TM-TM interactive motif is controlled at the sequence level, we compared two well characterized GXXXG motif-containing homodimers, those formed by human erythrocyte protein glycophorin A (GpA, high-affinity dimer) and those formed by bacteriophage M13 major coat protein (MCP, low affinity dimer). In both constructs, the GXXXG motif is necessary for TM-TM association. Although the remaining interfacial residues (underlined) in GpA ((LI) under bar XXG (V) under bar XXG (V) under bar XX (T) under bar) differ from those in MCP ( (VV) under bar XXG (A) under bar XXG (I) under bar XX (F) under bar), molecular modeling performed here indicated that GpA and MCP dimers possess the same overall fold. Thus, we could introduce GpA interfacial residues, alone and in combination, into the MCP sequence to help decrypt the determinants of dimer affinity. Using both in vivo TOXCAT assays and SDS-PAGE gel migration rates of synthetic peptides derived from TM regions of the proteins, we found that the most distal interfacial sites, 12 residues apart (and similar to18 Angstrom in structural space), work in concert to control TM-TM affinity synergistically.X119594sciescopu

Impoverished Diabetic Patients Whose Doctors Facilitate Their Participation in Medical Decision Making Are More Satisfied with Their Care

OBJECTIVE: Greater participation in medical decision making is generally advocated for patients, and often advocated for those with diabetes. Although some studies suggest that diabetic patients prefer to participate less in decision making than do healthy patients, the empirical relationship between such participation and diabetic patients' satisfaction with their care is currently unknown. We sought to characterize the relationship between aspects of diabetic patients' participation in medical decision making and their satisfaction with care. DESIGN: Cross-sectional observational study. SETTING: A general medical county hospital–affiliated clinic. PARTICIPANTS: One hundred ninety-eight patients with type 2 diabetes. MAIN MEASURES: Interviews conducted prior to the doctor visit assessed patients' desire to participate in medical decision making, baseline satisfaction (using a standardized measure), and sociodemographic and clinical characteristics. Postvisit interviews of those patients assessed their visit satisfaction and perception of their doctor's facilitation of patient involvement in care. A discrepancy score was computed for each subject to reflect the difference between the previsit stated desire regarding participation and the postvisit report of their experience of participation. RESULTS: Overall, patients reported low postvisit satisfaction relative to national standards (mean of 70 on a 98-point scale). Patients perceived a high level of facilitation of participation (mean 88 on a 100-point scale). Facilitation of participation and the discrepancy score both independently predicted greater visit satisfaction. In particular, a 13-point (1 SD) increase in the perceived facilitation score resulted in a 12-point (0.87 SD) increase in patient satisfaction, and a 1.22 point increase (1 SD) in the discrepancy score (the extent to which the patient was allowed more participation than, at previsit, he or she desired) resulted in a 6-point (0.5 SD) increase in the satisfaction score, even after controlling for initial desire to participate. For women, but not for men, physician facilitation of participation was a positive predictor of satisfaction; for men, but not women, desire to participate was a significant positive predictor of visit satisfaction. CONCLUSION: Clinicians may feel reassured that encouraging even initially reluctant patients with diabetes to participate in medical decision making may be associated with increased patient satisfaction. Greater patient participation has the potential to improve diabetic self-care because of the likely positive effect of patient satisfaction on adherence to treatment. Further research to assess the prospective effects of enhancing physician facilitation of patient participation is likely to yield important information for the effective treatment of chronically ill patients

An Anti-β-Amyloid Vaccine for Treating Cognitive Deficits in a Mouse Model of Down Syndrome

<div><p>In Down syndrome (DS) or trisomy of chromosome 21, the β-amyloid (Aβ) peptide product of the amyloid precursor protein (APP) is present in excess. Evidence points to increased <i>APP</i> gene dose and Aβ as playing a critical role in cognitive difficulties experienced by people with DS. Particularly, Aβ is linked to the late-life emergence of dementia as associated with neuropathological markers of Alzheimer’s disease (AD). At present, no treatment targets Aβ–related pathogenesis in people with DS. Herein we used a vaccine containing the Aβ 1–15 peptide embedded into liposomes together with the adjuvant monophosphoryl lipid A (MPLA). Ts65Dn mice, a model of DS, were immunized with the anti-Aβ vaccine at 5 months of age and were examined for cognitive measures at 8 months of age. The status of basal forebrain cholinergic neurons and brain levels of APP and its proteolytic products were measured. Immunization of Ts65Dn mice resulted in robust anti-Aβ IgG titers, demonstrating the ability of the vaccine to break self-tolerance. The vaccine-induced antibodies reacted with Aβ without detectable binding to either APP or its C-terminal fragments. Vaccination of Ts65Dn mice resulted in a modest, but non-significant reduction in brain Aβ levels relative to vehicle-treated Ts65Dn mice, resulting in similar levels of Aβ as diploid (2N) mice. Importantly, vaccinated Ts65Dn mice showed resolution of memory deficits in the novel object recognition and contextual fear conditioning tests, as well as reduction of cholinergic neuron atrophy. No treatment adverse effects were observed; vaccine did not result in inflammation, cellular infiltration, or hemorrhage. These data are the first to show that an anti-Aβ immunotherapeutic approach may act to target Aβ-related pathology in a mouse model of DS.</p></div