Identity of the elusive IgM Fc receptor (FcμR) in humans

Although Fc receptors (FcRs) for switched immunoglobulin (Ig) isotypes have been extensively characterized, FcR for IgM (FcμR) has defied identification. By retroviral expression and functional cloning, we have identified a complementary DNA (cDNA) encoding a bona fide FcμR in human B-lineage cDNA libraries. FcμR is defined as a transmembrane sialoglycoprotein of ∼60 kD, which contains an extracellular Ig-like domain homologous to two other IgM-binding receptors (polymeric Ig receptor and Fcα/μR) but exhibits an exclusive Fcμ-binding specificity. The cytoplasmic tail of FcμR contains conserved Ser and Tyr residues, but none of the Tyr residues match the immunoreceptor tyrosine-based activation, inhibitory, or switch motifs. Unlike other FcRs, the major cell types expressing FcμR are adaptive immune cells, including B and T lymphocytes. After antigen-receptor ligation or phorbol myristate acetate stimulation, FcμR expression was up-regulated on B cells but was down-modulated on T cells, suggesting differential regulation of FcμR expression during B and T cell activation. Although this receptor was initially designated as Fas apoptotic inhibitory molecule 3, or TOSO, our results indicate that FcμR per se has no inhibitory activity in Fas-mediated apoptosis and that such inhibition is only achieved when anti-Fas antibody of an IgM but not IgG isotype is used for inducing apoptosis

Cardiac troponin and heart failure in the era of high-sensitivity assays

AbstractThe Joint European Society of Cardiology-American College of Cardiology Foundation-American Heart Association-World Heart Federation Task Force for the Redefinition of Myocardial Infarction recommends cardiac troponin (cTn)-T as a first-line biomarker, and suggests the use of the 99th percentile of a reference population with acceptable precision (i.e. a coefficient of variance ≤10%) as a cut-off for the diagnosis of acute myocardial infarction. Recently developed troponin assays fulfill this analytical precision. While conventional cTnT assays have often been used as a positive or negative categorical variable, stepwise rises in high sensitivity (Hs)-cTnT in patients presenting with chronic heart failure (HF) have been associated with a progressive increase in the incidence of cardiovascular events. Similar observations have been made in the general population. Hs-cTnT at baseline and during follow-up is a powerful predictor of cardiac events in patients with HF and in the general population. Whether it is the ideal biomarker remains to be confirmed, however. We review the potential contributions of TnT assays in the assessment of risk of HF, in HF, and in myocardial diseases that cause HF

The phospholipid flippase ATP9A is required for the recycling pathway from the endosomes to the plasma membrane

Type IV P-type ATPases (P4-ATPases) are phospholipid flippases that translocate phospholipids from the exoplasmic (or luminal) to the cytoplasmic leaflet of lipid bilayers. In Saccharomyces cerevisiae, P4-ATPases are localized to specific subcellular compartments and play roles in compartment-mediated membrane trafficking; however, roles of mammalian P4-ATPases in membrane trafficking are poorly understood. We previously reported that ATP9A, one of 14 human P4-ATPases, is localized to endosomal compartments and the Golgi complex. In this study, we found that ATP9A is localized to phosphatidylserine (PS)-positive early and recycling endosomes, but not late endosomes, in HeLa cells. Depletion of ATP9A delayed the recycling of transferrin from endosomes to the plasma membrane, although it did not affect the morphology of endosomal structures. Moreover, depletion of ATP9A caused accumulation of glucose transporter 1 in endosomes, probably by inhibiting their recycling. By contrast, depletion of ATP9A affected neither the early/late endosomal transport and degradation of epidermal growth factor (EGF) nor the transport of Shiga toxin B fragment from early/recycling endosomes to the Golgi complex. Therefore ATP9A plays a crucial role in recycling from endosomes to the plasma membrane

Intermittent infusions of carperitide or inotoropes in out-patients with advanced heart failure.

[Background]: The ambulatory treatment of advanced heart failure (HF) with intermittent infusions of inotropes or natriuretic peptide chosen immediately before each infusion has not been described. [Methods]: Between May 2005 and July 2009, we treated 11 patients presenting with advanced HF, who received a total of 369 infusions of carperitide, olprinone, dopamine, or dobutamine, once or twice weekly. The pharmaceutical was selected before each infusion based on the systolic blood pressure (BP). [Results]: Carperitide, olprinone, and catecholamines were administered to 8 (73 infusions of 0.030 ± 0.004 μg/kg/min for 3.3 ± 0.8 h), 4 (18 infusions of 0.070 ± 0.017 μg/kg/min for 3.3 ± 0.5 h), and 6 patients (278 infusions of 3.6 ± 1.9 μg/kg/min for 2.8 ± 1.0 h), respectively. No adverse effect requiring cessation of infusion was observed. Over a mean follow-up of 29.3 ± 28.8 months (range 2–104), 4 patients died, all from cardiac causes. The Kaplan–Meier cumulative survival rate was 69.3% at 20 months (median follow-up). Compared with the pre-infusion period, the duration and number of hospitalizations for management of HF were decreased by 73.9% (p = 0.017), and 51.9% (p = 0.007), respectively, during the treatment period, and the overall medical costs by 56.9% (p = 0.021). [Conclusions]: In this study population, intermittent drug infusions selected from inotropes or natriuretic peptide based on the baseline systolic BP significantly decreased the length and number of hospitalizations and costs, without increasing mortality. These results indicate that intermittent infusions might be one of the therapeutic options in advanced HF

Comparison between optical coherence tomography-guided and intravascular ultrasound-guided primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

journal articl