Anchoring of Surface Proteins to the Cell Wall of Staphylococcus aureus. III. Lipid II is an in vivo peptidoglycan substrate for sortase-catalyzed surface protein anchoring

Surface proteins of Staphylococcus aureus are anchored to the cell wall peptidoglycan by a mechanism requiring a C-terminal sorting signal with an LPXTG motif. Surface proteins are first synthesized in the bacterial cytoplasm and then transported across the cytoplasmic membrane. Cleavage of the N-terminal signal peptide of the cytoplasmic surface protein P1 precursor generates the extracellular P2 species, which is the substrate for the cell wall anchoring reaction. Sortase, a membrane-anchored transpeptidase, cleaves P2 between the threonine (T) and the glycine (G) of the LPXTG motif and catalyzes the formation of an amide bond between the carboxyl group of threonine and the amino group of cell wall cross-bridges. We have used metabolic labeling of staphylococcal cultures with [32P]phosphoric acid to reveal a P3 intermediate. The 32P-label of immunoprecipitated surface protein is removed by treatment with lysostaphin, a glycyl-glycine endopeptidase that separates the cell wall anchor structure. Furthermore, the appearance of P3 is prevented in the absence of sortase or by the inhibition of cell wall synthesis. 32P-Labeled cell wall anchor species bind to nisin, an antibiotic that is known to form a complex with lipid II. Thus, it appears that the P3 intermediate represents surface protein linked to the lipid II peptidoglycan precursor. The data support a model whereby lipid II-linked polypeptides are incorporated into the growing peptidoglycan via the transpeptidation and transglycosylation reactions of cell wall synthesis, generating mature cell wall-linked surface protein

Evidence-based Practice in Developmental Disabilities: What is it and Why Does it Matter?

Editors’ Note: As recipient of the 2005 OADD-RSIG Professional Award for Excellence in Research, and Friday morning keynote speaker at the 2005 Annual OADD conference, Adrienne Perry spoke about the importance of evidence-based practice in the field of developmental disabilities. This is a summary of that keynote address

Follow-Up Study of Youth Who Received EIBI as Young Children

Although early intensive behavioral intervention (EIBI) has been clearly shown to be evidence-based, there is very little information available regarding long-term outcomes, especially from community effectiveness studies. We present data on cognitive, adaptive, and autism severity measures from four time points (pre- and post-EIBI and two follow-up points) for a sample of 21 youth, currently aged 16 years on average (range = 13-20) who received EIBI as young children and who have been out of EIBI for a mean of 10 years (range = 8.5-14). Results show heterogeneous outcomes and a general pattern of stability since the end of EIBI, suggesting gains made in EIBI are maintained

Tau PET and multimodal brain imaging in patients at risk for chronic traumatic encephalopathy.

ObjectiveTo characterize individual and group-level neuroimaging findings in patients at risk for Chronic Traumatic Encephalopathy (CTE).MethodsEleven male patients meeting criteria for Traumatic Encephalopathy Syndrome (TES, median age: 64) underwent neurologic evaluation, 3-Tesla MRI, and PET with [18F]-Flortaucipir (FTP, tau-PET) and [11C]-Pittsburgh compound B (PIB, amyloid-PET). Six patients underwent [18F]-Fluorodeoxyglucose-PET (FDG, glucose metabolism). We assessed imaging findings at the individual patient level, and in group-level comparisons with modality-specific groups of cognitively normal older adults (CN). Tau-PET findings in patients with TES were also compared to a matched group of patients with mild cognitive impairment or dementia due to Alzheimer's disease (AD).ResultsAll patients with TES sustained repetitive head injury participating in impact sports, ten in American football. Three patients met criteria for dementia and eight had mild cognitive impairment. Two patients were amyloid-PET positive and harbored the most severe MRI atrophy, FDG hypometabolism, and FTP-tau PET binding. Among the nine amyloid-negative patients, tau-PET showed either mildly elevated frontotemporal binding, a "dot-like" pattern, or no elevated binding. Medial temporal FTP was mildly elevated in a subset of amyloid-negative patients, but values were considerably lower than in AD. Voxelwise analyses revealed a convergence of imaging abnormalities (higher FTP binding, lower FDG, lower gray matter volumes) in frontotemporal areas in TES compared to controls.ConclusionsMildly elevated tau-PET binding was observed in a subset of amyloid-negative patients at risk for CTE, in a distribution consistent with CTE pathology stages III-IV. FTP-PET may be useful as a biomarker of tau pathology in CTE but is unlikely to be sensitive to early disease stages

Deep-coverage whole genome sequences and blood lipids among 16,324 individuals.

Large-scale deep-coverage whole-genome sequencing (WGS) is now feasible and offers potential advantages for locus discovery. We perform WGS in 16,324 participants from four ancestries at mean depth >29X and analyze genotypes with four quantitative traits-plasma total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, and triglycerides. Common variant association yields known loci except for few variants previously poorly imputed. Rare coding variant association yields known Mendelian dyslipidemia genes but rare non-coding variant association detects no signals. A high 2M-SNP LDL-C polygenic score (top 5th percentile) confers similar effect size to a monogenic mutation (~30 mg/dl higher for each); however, among those with severe hypercholesterolemia, 23% have a high polygenic score and only 2% carry a monogenic mutation. At these sample sizes and for these phenotypes, the incremental value of WGS for discovery is limited but WGS permits simultaneous assessment of monogenic and polygenic models to severe hypercholesterolemia

A comparison of random vs. chemotaxis-driven contacts of T cells with dendritic cells during repertoire scanning

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83669/1/JTB_article.pd

Disclosing genetic risk for Alzheimer’s dementia to individuals with mild cognitive impairment

IntroductionThe safety of predicting conversion from mild cognitive impairment (MCI) to Alzheimer’s disease (AD) dementia using apolipoprotein E (APOE) genotyping is unknown.MethodsWe randomized 114 individuals with MCI to receive estimates of 3‐year risk of conversion to AD dementia informed by APOE genotyping (disclosure arm) or not (non‐disclosure arm) in a non‐inferiority clinical trial. Primary outcomes were anxiety and depression scores. Secondary outcomes included other psychological measures.ResultsUpper confidence limits for randomization arm differences were 2.3 on the State Trait Anxiety Index and 0.5 on the Geriatric Depression Scale, below non‐inferiority margins of 3.3 and 1.0. Moreover, mean scores were lower in the disclosure arm than non‐disclosure arm for test‐related positive impact (difference: ‐1.9, indicating more positive feelings) and AD concern (difference: ‐0.3).DiscussionProviding genetic information to individuals with MCI about imminent risk for AD does not increase risks of anxiety or depression and may provide psychological benefits.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154645/1/trc212002_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154645/2/trc212002.pd

Le FORUM, Vol. 39 No. 1

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