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THE JOURNAL OF BIOLOGICAL CHEMISTRY: The Biochemical Behavior of LeadL I. Influence of Calcium, Phosphorus, and Vitamin D on Lead in Blood and Bone

Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is an enzyme with important regulatory functions in the heart and brain, and its chronic activation can be pathological. CaMKII activation is seen in heart failure, and can directly induce pathological changes in ion channels, Ca(2+) handling and gene transcription. Here, in human, rat and mouse, we identify a novel mechanism linking CaMKII and hyperglycaemic signalling in diabetes mellitus, which is a key risk factor for heart and neurodegenerative diseases. Acute hyperglycaemia causes covalent modification of CaMKII by O-linked N-acetylglucosamine (O-GlcNAc). O-GlcNAc modification of CaMKII at Ser 279 activates CaMKII autonomously, creating molecular memory even after Ca(2+) concentration declines. O-GlcNAc-modified CaMKII is increased in the heart and brain of diabetic humans and rats. In cardiomyocytes, increased glucose concentration significantly enhances CaMKII-dependent activation of spontaneous sarcoplasmic reticulum Ca(2+) release events that can contribute to cardiac mechanical dysfunction and arrhythmias. These effects were prevented by pharmacological inhibition of O-GlcNAc signalling or genetic ablation of CaMKIIδ. In intact perfused hearts, arrhythmias were aggravated by increased glucose concentration through O-GlcNAc- and CaMKII-dependent pathways. In diabetic animals, acute blockade of O-GlcNAc inhibited arrhythmogenesis. Thus, O-GlcNAc modification of CaMKII is a novel signalling event in pathways that may contribute critically to cardiac and neuronal pathophysiology in diabetes and other diseases.

/pdf/diabetic-hyperglycaemia-activates-camkii-and-arrhythmias-by-35utscadg2.pdf

Diabetic hyperglycaemia activates CaMKII and arrhythmias by O-linked glycosylation

Inteins are auto-processing domains found in organisms from all domains of life. These proteins carry out a process known as protein splicing, which is a multi-step biochemical reaction comprised of both the cleavage and formation of peptide bonds. While the endogenous substrates of protein splicing are specific essential proteins found in intein-containing host organisms, inteins are also functional in exogenous contexts and can be used to chemically manipulate virtually any polypeptide backbone. Given this, protein chemists have exploited various facets of intein reactivity to modify proteins in myriad ways for both basic biological research as well as potential therapeutic applications. Here, we review the intein field, first focusing on the biological context and phylogenetic diversity of inteins, followed by a description of intein structure and biochemical function. Finally, we discuss prevalent intein-based technologies, focusing on their applications in chemical biology, followed by persistent caveats of intein chemistry and approaches to alleviate these shortcomings. The findings summarized herein describe two and a half decades of research, leading from a biochemical curiosity to the development of powerful protein engineering tools.

Inteins: nature's gift to protein chemists

The binding between biotin and streptavidin or avidin is one of the strongest known non-covalent biological interactions. The (strept)avidin-biotin interaction has been widely used for decades in biological research and biotechnology. Therefore labeling of purified proteins by biotin is a powerful way to achieve protein capture, immobilization, and functionalization, as well as multimerizing or bridging molecules. Chemical biotinylation often generates heterogeneous products, which may have impaired function. Enzymatic biotinylation with E. coli biotin ligase (BirA) is highly specific in covalently attaching biotin to the 15 amino acid AviTag peptide, giving a homogeneous product with high yield. AviTag can conveniently be added genetically at the N-terminus, C-terminus, or in exposed loops of a target protein. We describe here procedures for AviTag insertion by inverse PCR, purification of BirA fused to glutathione-S-transferase (GST-BirA) from E. coli, BirA biotinylation of purified protein, and gel-shift analysis by SDS-PAGE to quantify the extent of biotinylation.

Site-specific biotinylation of purified proteins using BirA.

Programmed connection of amino acids or nucleotides into chains introduced a revolution in control of biological function. Reacting proteins together is more complex because of the number of reactive groups and delicate stability. Here we achieved sequence-programmed irreversible connection of protein units, forming polyprotein teams by sequential amidation and transamidation. SpyTag peptide is engineered to spontaneously form an isopeptide bond with SpyCatcher protein. By engineering the adhesin RrgA from Streptococcus pneumoniae, we developed the peptide SnoopTag, which formed a spontaneous isopeptide bond to its protein partner SnoopCatcher with >99% yield and no cross-reaction to SpyTag/SpyCatcher. Solid-phase attachment followed by sequential SpyTag or SnoopTag reaction between building-blocks enabled iterative extension. Linear, branched, and combinatorial polyproteins were synthesized, identifying optimal combinations of ligands against death receptors and growth factor receptors for cancer cell death signal activation. This simple and modular route to programmable “polyproteams” should enable exploration of a new area of biological space.

/pdf/programmable-polyproteams-built-using-twin-peptide-17eaa077mh.pdf

Programmable polyproteams built using twin peptide superglues.

Unprecedented Rates and Efficiencies Revealed for New Natural Split Inteins from Metagenomic Sources

Isoform specific regulation of the inositol 1,4,5-trisphosphate receptor by O-linked glycosylation

C-terminal Domain of Chromogranin B Regulates Intracellular Calcium Signaling

Transthoracic and transesophageal echocardiography are important investigations in the intensive care unit (ICU) to diagnose acute cardiac pathologies and assess the haemodynamic status. Recommendations for critical care echocardiography (CCE) have been published recently, but these still lack an evidence-based foundation. It is not known if performing transthoracic echocardiography (TTE) on a routine basis instead of only when required in acute cases is feasible or clinically useful. In this single-centre prospective observational study, we routinely performed TTE on 111 consecutive non-cardiological, non-cardiothoracic surgical ICU patients in two surgical ICUs in a tertiary care facility. Significant cardiac pathologies were detected in 82 (76.6%) and critical cardiac pathologies in 33 (30.8%) of the 107 patients. The most common critical cardiac pathologies were sPAP > 50 mmHg (19.63%), tricuspid annular plane systolic excursion ≤ 13 mm (9.4%), grade III diastolic dysfunction (8.4%), severe tricuspid valve insufficiency (5.6%) and left ventricular ejection fraction (LV-EF) ˂ 30% (4.7%). Some of the most commonly found cardiac pathologies are not well emphasised in current recommendations and training programs. We observed a progression of the cardiac pathologies previously described in 41 of the patients (91.1%). Patients with echocardiographic abnormalities had a significant survival disadvantage in the ICU. By performing CCE routinely, we observed the range and prevalence of cardiac pathologies that can be detected by echocardiography in critically ill patients. We recommend routine transthoracic CCE in ICU patients for early detection of cardiac pathologies and to help inform early intervention regimens, since cardiac conditions carry a significant survival disadvantage for the ICU patient.

https://www.mdpi.com/2075-4418/10/9/671/pdf

Critical Care Echocardiography as a Routine Procedure for the Detection and Early Treatment of Cardiac Pathologies.

https://www.cell.com/neuron/pdf/S0896-6273(10)00981-5.pdf

Unloading Intracellular Calcium Stores Reveals Regionally Specific Functions

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