Hdm2 nuclear export, regulated by insulin-like growth factor-I/MAPK/p90Rsk signaling, mediates the transformation of human cells

Insulin-like growth factor (IGF)-I receptor activation leads to enhanced proliferation and cell survival via the MAP kinase and phosphatidylinositol 3-kinase-signaling pathways. Upon stimulation by IGF-I, the Hdm2 oncoprotein is phosphorylated by AKT, leading to its rapid nuclear translocation and subsequent inhibition of p53. We now show that IGF-I stimulation regulates the nuclear export of Hdm2 and p53 via the MAP kinase pathway. Inhibition of p38 MAPK or MEK via pharmacological means or expression of dominant negative proteins inhibited the cytoplasmic accumulation of Hdm2 and increased Hdm2 and p53 protein levels, whereas constitutively active p90Rsk promoted the nuclear export of Hdm2. Expression of constitutively active p90Rsk with E1A, oncogenic H-Ras, and hTERT resulted in the anchorage-independent growth of normal human fibroblasts. Our findings link p90Rsk-mediated modulation of Hdm2 nuclear to cytoplasmic shuttling with the diminished ability of p53 to regulate cell cycle checkpoints that ultimately leads to transformation.     

Pediatric Invasive Pneumococcal Disease Caused by Vaccine Serotypes following the Introduction of Conjugate Vaccination in Denmark

A seven-valent pneumococcal conjugate vaccine (PCV7) was introduced in the Danish childhood immunization program (2+1 schedule) in October 2007, followed by PCV13 starting from April 2010. The nationwide incidence of IPD among children younger than 5 years nearly halved after the introduction of PCV7 in the program, mainly due to a decline in IPD caused by PCV7-serotypes. We report the results from a nationwide population-based cohort study of laboratory confirmed IPD cases in children younger than 5 years during October 1, 2007 to December 31, 2010 and describe the characteristics of children suspected to present with a vaccine failure. The period between April 19 and December 31, 2010 was considered a PCV7/PCV13 transitional period, where both vaccines were offered. We identified 45 episodes of IPD caused by a PCV7 serotype (23% of the total number) and 105 (55%) caused by one of the 6 additional serotypes in PCV13. Ten children had received at least one PCV7 dose before the onset of IPD caused by a PCV7 serotype. Seven children were considered to be incompletely vaccinated before IPD, but only three cases fulfilled the criteria of vaccine failure (caused by serotypes 14, 19F and 23F). One case of vaccine failure was observed in a severely immunosuppressed child following three PCV7 doses, and two cases were observed in immunocompetent children following two infant doses before they were eligible for their booster. None of the IPD cases caused by the additional PCV13 serotypes had been vaccinated by PCV13 and there were therefore no PCV13-vaccine failures in the first 8-months after PCV13 introduction in Denmark.     

New resource for the computation of cartilage biphasic material properties with the interpolant response surface method

Cartilage material properties are important for understanding joint function and diseases, but can be challenging to obtain. Three biphasic material properties (aggregate modulus, Poisson's ratio and permeability) can be determined using an analytical or finite element model combined with optimisation to find the material properties values that best reproduce an experimental creep curve. The purpose of this study was to develop an easy-to-use resource to determine biphasic cartilage material properties. A Cartilage Interpolant Response Surface was generated from interpolation of finite element simulations of creep indentation tests. Creep indentation tests were performed on five sites across a tibial plateau. A least-squares residual search of the Cartilage Interpolant Response Surface resulted in a best-fit curve for each experimental condition with corresponding material properties. These sites provided a representative range of aggregate moduli (0.48–1.58 MPa), Poisson's ratio (0.00–0.05) and permeability (1.7 × 10^? 15–5.4 × 10^? 15 m⁴/N s) values found in human cartilage. The resource is freely available from https://simtk.org/home/va-squish.     

Is Rapoport's rule a recent phenomenon? A deep time perspective on potential causal mechanisms

Macroecology strives to identify ecological patterns on broad spatial and temporal scales. One such pattern, Rapoport''s rule, describes the tendency of species'' latitudinal ranges to increase with increasing latitude. Several mechanisms have been proposed to explain this rule. Some invoke climate, either through glaciation driving differential extinction of northern species or through increased seasonal variability at higher latitudes causing higher thermal tolerances and subsequently larger ranges. Alternatively, continental tapering or higher interspecific competition at lower latitudes may be responsible. Assessing the incidence of Rapoport''s rule through deep time can help to distinguish between competing explanations. Using fossil occurrence data from the Palaeobiology Database, we test these hypotheses by evaluating mammalian compliance with the rule throughout the Caenozoic of North America. Adherence to Rapoport''s rule primarily coincides with periods of intense cooling and increased seasonality, suggesting that extinctions caused by changing climate may have played an important role in erecting the latitudinal gradients in range sizes seen today.     

The ERdj5-Sel1L complex facilitates cholera toxin retrotranslocation

Cholera toxin (CT) traffics from the host cell surface to the endoplasmic reticulum (ER), where the toxin''s catalytic CTA1 subunit retrotranslocates to the cytosol to induce toxicity. In the ER, CT is captured by the E3 ubiquitin ligase Hrd1 via an undefined mechanism to prepare for retrotranslocation. Using loss-of-function and gain-of-function approaches, we demonstrate that the ER-resident factor ERdj5 promotes CTA1 retrotranslocation, in part, via its J domain. This Hsp70 cochaperone regulates binding between CTA and the ER Hsp70 BiP, a chaperone previously implicated in toxin retrotranslocation. Importantly, ERdj5 interacts with the Hrd1 adaptor Sel1L directly through Sel1L''s N-terminal lumenal domain, thereby linking ERdj5 to the Hrd1 complex. Sel1L itself also binds CTA and facilitates toxin retrotranslocation. By contrast, EDEM1 and OS-9, two established Sel1L binding partners, do not play significant roles in CTA1 retrotranslocation. Our results thus identify two ER factors that promote ER-to-cytosol transport of CTA1. They also indicate that ERdj5, by binding to Sel1L, triggers BiP–toxin interaction proximal to the Hrd1 complex. We postulate this scenario enables the Hrd1-associated retrotranslocation machinery to capture the toxin efficiently once the toxin is released from BiP.     

Pharmacological Targeting of Native CatSper Channels Reveals a Required Role in Maintenance of Sperm Hyperactivation

The four sperm-specific CatSper ion channel proteins are required for hyperactivated motility and male fertility, and for Ca²⁺ entry evoked by alkaline depolarization. In the absence of external Ca²⁺, Na⁺ carries current through CatSper channels in voltage-clamped sperm. Here we show that CatSper channel activity can be monitored optically with the [Na⁺]_i-reporting probe SBFI in populations of intact sperm. Removal of external Ca²⁺ increases SBFI signals in wild-type but not CatSper2-null sperm. The rate of the indicated rise of [Na⁺]_i is greater for sperm alkalinized with NH₄Cl than for sperm acidified with propionic acid, reflecting the alkaline-promoted signature property of CatSper currents. In contrast, the [Na⁺]_i rise is slowed by candidate CatSper blocker HC-056456 (IC₅₀ ∼3 µM). HC-056456 similarly slows the rise of [Ca²⁺]_i that is evoked by alkaline depolarization and reported by fura-2. HC-056456 also selectively and reversibly decreased CatSper currents recorded from patch-clamped sperm. HC-056456 does not prevent activation of motility by HCO₃ ⁻ but does prevent the development of hyperactivated motility by capacitating incubations, thus producing a phenocopy of the CatSper-null sperm. When applied to hyperactivated sperm, HC-056456 causes a rapid, reversible loss of flagellar waveform asymmetry, similar to the loss that occurs when Ca²⁺ entry through the CatSper channel is terminated by removal of external Ca²⁺. Thus, open CatSper channels and entry of external Ca²⁺ through them sustains hyperactivated motility. These results indicate that pharmacological targeting of the CatSper channel may impose a selective late-stage block to fertility, and that high-throughput screening with an optical reporter of CatSper channel activity may identify additional selective blockers with potential for male-directed contraception.     

From Transient to Steady-state Response of Ecosystems to Atmospheric CO2-enrichment and Global Climate Change: Conceptual Challenges and Need for an Integrated Approach

Evidence continues to accumulate that humans are significantly increasing atmospheric CO₂ concentrations, resulting in unprecedented changes in the global climate system. Experimental manipulations of terrestrial ecosystems and their components have greatly increased our understanding of short-term responses to these global perturbations and have provided valuable input to ecosystem, dynamic vegetation, and global scale models. However, concerns exist that these initial experimental responses may be transitory, thereby limiting our ability to extrapolate short-term experimental responses to infer longer-term effects. To do these extrapolations, it will be necessary to understand changes in response patterns over time, including alterations in the magnitude, direction, and rate of change of the responses. These issues represent one of our largest challenges in accurately predicting longer-term changes in ecosystems and associated feedbacks to the climate system. Key issues that need to be considered when designing future experiments or refining models include: linear vs. non-linear responses, direct vs. indirect effects, lags in response, acclimation, resource limitation, homeostasis, buffers, thresholds, ecosystem stoichiometry, turnover rates and times, and alterations in species composition. Although experimental and landscape evidence for these response patterns exist, extrapolating longer-term response patterns from short-term experiments will ultimately require a unified multidisciplinary approach, including better communication and collaboration between theoreticists, experimentalists and modelers.