BiP Binding to the ER-Stress Sensor Ire1 Tunes the Homeostatic Behavior of the Unfolded Protein Response

The unfolded protein response (UPR) is an intracellular signaling pathway that counteracts variable stresses that impair protein folding in the endoplasmic reticulum (ER). As such, the UPR is thought to be a homeostat that finely tunes ER protein folding capacity and ER abundance according to need. The mechanism by which the ER stress sensor Ire1 is activated by unfolded proteins and the role that the ER chaperone protein BiP plays in Ire1 regulation have remained unclear. Here we show that the UPR matches its output to the magnitude of the stress by regulating the duration of Ire1 signaling. BiP binding to Ire1 serves to desensitize Ire1 to low levels of stress and promotes its deactivation when favorable folding conditions are restored to the ER. We propose that, mechanistically, BiP achieves these functions by sequestering inactive Ire1 molecules, thereby providing a barrier to oligomerization and activation, and a stabilizing interaction that facilitates de-oligomerization and deactivation. Thus BiP binding to or release from Ire1 is not instrumental for switching the UPR on and off as previously posed. By contrast, BiP provides a buffer for inactive Ire1 molecules that ensures an appropriate response to restore protein folding homeostasis to the ER by modulating the sensitivity and dynamics of Ire1 activity.     

Joint synchrony of reciprocal hormonal signaling in human paradigms of both ACTH excess and cortisol depletion

The hypothalamo-pituitary-adrenal axis is a stress-adaptive neuroendocrine ensemble, in which adrenocorticotropin (ACTH) drives cortisol secretion (feedforward) and cortisol restrains ACTH outflow (feedback). Quantifying direction- and pathway-specific adjustments within this and other interlinked systems by noninvasive means remains difficult. The present study tests the hypothesis that forward and reverse cross-approximate entropy (X-ApEn), a lag-, scale-, and model-independent measure of two-signal synchrony, would allow quantifiable discrimination of feedforward (ACTH --> cortisol) and feedback (cortisol --> ACTH) control. To this end, forward X-ApEn was defined by employing serial ACTH concentrations as a template to appraise pair-wise synchrony with cortisol secretion rates and vice versa for reverse X-ApEn. Coupled hormone profiles included normal ACTH-normal cortisol, high ACTH-high cortisol, and high ACTH-low cortisol concentrations in 35 healthy subjects, 21 patients with tumoral ACTH secretion, and 9 volunteers given placebo and a steroidogenic inhibitor, respectively. We used forward and reverse X-ApEn analyses to identify marked and equivalent losses of feedforward and feedback linkages (both P < 0.001) in patients with tumoral ACTH secretion. An identical analytical strategy revealed that ACTH --> cortisol feedforward synchrony decreases (P < 0.001), whereas cortisol --> ACTH feedback synchrony increases (P < 0.001), in response to hypocortisolemia. The collective outcomes establish precedence for pathway-specific adaptations in a major neurohormonal system. Thus quantification of directionally defined joint synchrony of biologically coupled signals offers a noninvasive strategy to dissect feedforward- and feedback-selective adaptations in an interactive axis.     

Immunological characteristics associated with the protective efficacy of antibodies to ricin

A/B toxins, produced by bacteria and plants, are among the deadliest molecules known. The B chain binds the cell, whereas the A chain exerts the toxic effect. Both anti-A chain and anti-B chain Abs can neutralize toxins in vivo and in vitro. B chain Abs block binding of the toxin to the cell. It is not known how anti-A chain Abs function. Working with ricin toxin, we demonstrate that immunization with A chain induces greater protection than immunization with B chain. A panel of mAbs, binding to A chain, B chain, or both chains, has been produced and characterized. Immunologic characteristics evaluated include isotype, relative avidity, and epitope specificity. The ability to inhibit ricin enzymatic or cell binding activity was studied, as was the ability to block ricin-mediated cellular cytotoxicity on human and murine cell lines. Finally, the in vivo protective efficacy of the Abs in mice was studied. The Ab providing the greatest in vivo protective efficacy was directed against the A chain. It had the greatest relative avidity and the greatest ability to block enzymatic function and neutralize cytotoxicity. Interestingly, we also obtained an anti-A chain Ab that bound with high avidity, blocked enzymatic activity, did not neutralize cytotoxicity, and actually enhanced the in vivo toxicity of ricin. Anti-A chain Abs with moderate avidity had no in vivo effect, nor did any anti-B chain Abs.     

Utility of the Framingham risk score to predict the presence of coronary atherosclerosis in patients with rheumatoid arthritis

The prevalence of ischemic heart disease and atherosclerosis is increased in patients with rheumatoid arthritis (RA). In the general population, but not in patients with systemic lupus erythematosus, the Framingham risk score identifies patients at increased cardiovascular risk and helps determine the need for preventive interventions. We examined the hypothesis that the Framingham score is increased and associated with coronary-artery atherosclerosis in patients with RA. The Framingham score and the 10-year cardiovascular risk were compared among 155 patients with RA (89 with early disease, 66 with long-standing disease) and 85 control subjects. The presence of coronary-artery calcification was determined by electron-beam computed tomography. The Framingham score was compared in patients with RA and control subjects, and the association between the risk score and coronary-artery calcification was examined in patients. Patients with long-standing RA had a higher Framingham score (14 [11 to 18]) (median [interquartile range]) compared to patients with early RA (11 [8 to 14]) or control subjects (12 [7 to 14], P < 0.001). This remained significant after adjustment for age and gender (P = 0.015). Seventy-six patients with RA had coronary calcification; their Framingham risk score was higher (14 [12 to 17]) than that of 79 patients without calcification (10 [5 to 14]) (P < 0.001). Furthermore, a higher Framingham score was associated with a higher calcium score (odds ratio [OR] = 1.20, 95% confidence interval [CI] 1.12 to 1.29, P < 0.001), and the association remained significant after adjustment for age and gender (OR = 1.15, 95% CI 1.02 to 1.29, P = 0.03). In conclusion, a higher Framingham risk score is independently associated with the presence of coronary calcification in patients with RA.     

Identification and Characterization of a Broadly Cross-Reactive HIV-1 Human Monoclonal Antibody That Binds to Both gp120 and gp41

Identification of broadly cross-reactive HIV-1-neutralizing antibodies (bnAbs) may assist vaccine immunogen design. Here we report a novel human monoclonal antibody (mAb), designated m43, which co-targets the gp120 and gp41 subunits of the HIV-1 envelope glycoprotein (Env). M43 bound to recombinant gp140 s from various primary isolates, to membrane-associated Envs on transfected cells and HIV-1 infected cells, as well as to recombinant gp120 s and gp41 fusion intermediate structures containing N-trimer structure, but did not bind to denatured recombinant gp140 s and the CD4 binding site (CD4bs) mutant, gp120 D368R, suggesting that the m43 epitope is conformational and overlaps the CD4bs on gp120 and the N-trimer structure on gp41. M43 neutralized 34% of the HIV-1 primary isolates from different clades and all the SHIVs tested in assays based on infection of peripheral blood mononuclear cells (PBMCs) by replication-competent virus, but was less potent in cell line-based pseudovirus assays. In contrast to CD4, m43 did not induce Env conformational changes upon binding leading to exposure of the coreceptor binding site, enhanced binding of mAbs 2F5 and 4E10 specific for the membrane proximal external region (MPER) of gp41 Envs, or increased gp120 shedding. The overall modest neutralization activity of m43 is likely due to the limited binding of m43 to functional Envs which could be increased by antibody engineering if needed. M43 may represent a new class of bnAbs targeting conformational epitopes overlapping structures on both gp120 and gp41. Its novel epitope and possibly new mechanism(s) of neutralization could helpdesign improved vaccine immunogens and candidate therapeutics.     

THE GEOTROPIC CONDUCT OF YOUNG RATS

On page 263, Vol. x, No. 2, November 20, 1926, under Curve A, in the legend for Fig. 3, Ordinate scale at the left should read Ordinate scale at the right. Under Curve B, Ordinate scale at the right should read Ordinate scale at the left.     

African Indigenous Vegetable Seed Systems in Western Kenya

Economic Botany - African indigenous vegetable (AIV) production systems are often constrained by the availability of high-quality seed. Concerted efforts to improve the informal seed sector could...     

TEMPERATURE CHARACTERISTICS FOR FREQUENCY OF RESPIRATORY MOVEMENTS IN YOUNG MAMMALS

The internal temperature of 2 day old mice deviates by +0.01° to +3.0°C. from the environmental temperature over a range of 24°. The undeveloped temperature control allows rhythmic activities in this mammalian material to be readily subjected to the analysis afforded by temperature characteristics, and thus makes possible some insight into the physicochemical events controlling vital processes in entire uninjured mammals. The thermal increments and critical temperatures obtained point to a similarity in the controlling system of reactions for both homothermic and poikilothermic organisms. For frequency of respiratory movements the increments 12,340 (19.6° to 35.2°C.); 28,340 or 36,500 (15.5° to 19.6°C.) are most frequently found (thirteen cases). Rarely µ = 8,450, 33,000, or 18,340 (two cases). The last increment is either associated with µ = 36,000 below 20°, or extends unbroken throughout the whole range (one case).