Cadmium-induced autophagy and apoptosis are mediated by a calcium signaling pathway

The cytotoxicity of cadmium (Cd) induced autophagy and apoptosis in MES-13 cells was determined by flow cytometry. Autophagy was also assessed by formation of autophagosomes and processing of LC3. Pharmacological inhibition of autophagy resulted in increased of cell viability, suggesting autophagy plays a role in cell death in Cd-treated mesangial cells. Cd also induced a rapid elevation in cytosolic calcium ([Ca²⁺]_i ), and modulation of [Ca²⁺]_i via treatment with IP ₃R inhibitor or knockdown of calcineurin resulted in a change in the proportion of cell death, suggesting that the release of calcium from the ER plays a crucial role in Cd-induced cell death. Inhibition of Cd-induced ERK activation by PD 98059 suppressed Cd-induced autophagy, and BAPTA-AM eliminated activation of ERK. BAPTA-AM also inhibited Cd-induced mitochondrial depolarization and activation of caspases. These findings demonstrated that Cd induces both autophagy and apoptosis through elevation of [Ca²⁺]_i, followed by Ca²⁺-ERK and Ca²⁺-mitochondria-caspase signaling pathways. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Received 05 July 2008; received after revision 25 August 2008; accepted 17 September 2008     

Membrane translocation and oligomerization of hBok are triggered in response to apoptotic stimuli and Bnip3

hBok is a human pro-apoptotic member of the Bcl-2 family. By fluorescence in situ hybridization and in silico analysis, hBok was found to be located on chromosome 2q37.3. Its expression was detected in various organs and several hormonally regulated cancer cells. Expression of hBok was shown to be upregulated in estrogen-dependent breast cancer by estrogen deprivation and in myocardial cells during hypoxia. Confocal laser scanning microscopy examinations and subcellular fractionation studies showed that hBok was distributed in both the cytosol and intracellular membranes of healthy cells. Upon overexpression of hBok or stimulation of apoptosis, hBok became integrated into the membrane. Furthermore, apoptosis and oligomerization were promoted by BH3-only proteins, such as Bid, Bnip3 and p53, but prevented by BFL-1. hBok was found to interact with Bnip3. Our findings suggest that functional BH3-only proteins facilite the oligomerization and insertion of hBok into the membrane to activate it.Received 7 December 2004; received after revision 23 February 2005; accepted 4 March 2005     

Age differences in the cellular response to cerebral lesions in the dog and mouse

Zusammenfassung Die zelluläre Reaktion an traumatischen, mechanisch gesetzten Läsionen in der Gehirnrinde wurde an neugeborenen und erwachsenen Hunden sowie an Mäusen untersucht. Die Heilung der Läsionen in Neugeborenen war so, dass das Gehirngewebe makroskopisch normal aussah; histologisch waren die durchtrennten Elemente durch die Heilungsprozesse unter minimaler glialer Reaktion wieder gut reorganisiert.     

Language understanding is grounded in experiential simulations: a response to Weiskopf

Several disciplines within the cognitive sciences have advanced the idea that people comprehend the actions of others, including the linguistic meanings they communicate, through embodied simulations where they imaginatively recreate the actions they observe or hear about. This claim has important consequences for theories of mind and meaning, such as that people’s use and interpretation of language emerges as a kind of bodily activity that is an essential part of ordinary cognition. Daniel Weiskopf presents several arguments against the idea that experiential simulations play a major role in immediate language use and meaning. We offer several rebuttals to Weiskopf, in which we critique his interpretation of simulation theory, present additional psycholinguistic evidence supportive of the simulation perspective, and suggest that a more traditional theory of linguistic meaning and processing has little psychological and empirical validity.     

Recruitment of Pyk2 to SHPS-1 signaling complex is required for IGF-I-dependent mitogenic signaling in vascular smooth muscle cells

In vascular smooth muscle cells, IGF-I stimulates SHPS-1/SHP2/Src complex formation which is required for IGF-I-stimulated cell proliferation. Using SHP2/Src silencing and a Pyk2/Y402F mutant, we showed that Pyk2 was also recruited to the SHPS-1 complex. Pyk2 recruitment to SHPS-1 is mediated via the interaction of Pyk2 Tyr402 and the Src in response to IGF-I. Following Src/Pyk2 association, Src phosphorylates Pyk2 on Tyr881 providing a binding site for Grb2. Cells expressing Pyk2/Y881F showed decreased Grb2 recruitment to SHPS-1 and impaired Shc/Grb2 association. This change led to reduced Erk1/2 (MAP kinase) activation and cell proliferation in response to IGF-I. Our results show that, following its recruitment to the SHPS-1 signaling complex, Pyk2 localizes Grb2 in close proximity to Shc thereby facilitating Shc/Grb2 association which leads to Erk1/2 activation in response to IGF-I. Thus, Pyk2 recruitment to SHPS-1 plays an important role in regulating the IGF-I-stimulated mitogenic response.     

The decremental propagation of the action potential and loss of mechanical response in frog sartorius muscle in the absence of calcium

Zusammenfassung Die Herabsetzung der Kontraktionsleistung einer Sartoriusmuskelfaser des Frosches, bevor sie wegen Calciummangel elektrisch unerregbar wird, kann weitgehend mit einer ungenügenden Aktivierung des kontraktilen Systems durch das Abklingen des Aktionspotentials erklärt werden.

---

---

On leave of absence from Human Biomechanics Laboratory, Medical Research Council, Hampstead, London (England).     

The STING pathway and regulation of innate immune signaling in response to DNA pathogens

The innate immune system has evolved a variety of sensing mechanisms to detect and counter microbial invasion. These include the Toll-like receptor (TLR), cytoplasmic, nucleotide binding oligomerization domain (NOD)-like receptor and RIG-I-like helicase (RLH) pathways. However, how the cell detects pathogen-associated DNA to trigger host defense, including the production of interferon, remains to be fully clarified. Understanding these processes could have profound implications into how we understand and treat a variety of microbial-related disease, including viral-associated cancers, as well as autoimmune disorders. Recently, an endoplasmic reticulum-associated molecule referred to as STING (for stimulator of interferon genes) was isolated and shown to be critical for regulating the production of IFN in response to cytoplasmic DNA. Here, we review recent discoveries relating to the detection of foreign DNA, including the importance of the STING and inflammasome pathways and the triggering of innate signaling processes.     

Zebrafish rgs4 is essential for motility and axonogenesis mediated by Akt signaling

The schizophrenia susceptibility gene, Rgs4, is one of the most intensively studied regulators of G-protein signaling members, well known to be fundamental in regulating neurotransmission. However, little is known about its role in the developing nervous system. We have isolated zebrafish rgs4 and shown that it is transcribed in the developing nervous system. Rgs4 knockdown did not affect neuron number and patterning but resulted in locomotion defects and aberrant development of axons. This was confirmed using a selective Rgs4 inhibitor, CCG-4986. Rgs4 knockdown also attenuated the level of phosphorylated-Akt1, and injection of constitutively-activated AKT1 rescued the motility defects and axonal phenotypes in the spinal cord but not in the hindbrain and trigeminal neurons. Our in vivo analysis reveals a novel role for Rgs4 in regulating axonogenesis during embryogenesis, which is mediated by another schizophrenia-associated gene, Akt1, in a region-specific manner.     

The role of calcium and zinc in the electrical and mechanical responses of frog sartorius muscle

Zusammenfassung Membranpotential, Aktionspotential und Spannung der Einzelzuckung einer Einzelfaser des M. sartorius vonRana temporaria nehmen in der calciumfreien Badeflüssigkeit progressiv ab. Extrazelluläres Zink hingegen ist für die Kontraktion nicht notwendig, beeinflusst aber in physiologischen Konzentrationen die Dauer der Aktivität.     

Modulation of signal transduction through the cellular prion protein is linked to its incorporation in lipid rafts

Because expressed at a significant level at the membrane of human T cells, we made the hypothesis that the cellular prion protein (PrP^c) could behave as a receptor, and be responsible for signal transduction. PrP^c engagement by specific antibodies was observed to induce an increase in cytosolic calcium concentration and led to enhanced activity of Src protein tyrosine kinases. Antibodies to CD4 and CD59 did not influence calcium fluxes or signaling. The effect was maximal after the formation of a network involving avidin and biotinylated antibody to PrP^c and was inhibited after raft disruption. PrP^c localization was not restricted to rafts in resting cells but engagement was a prerequisite for signaling induction, with concomitant PrP^c recruitment into rafts. These results suggest a role for PrP^c in signaling pathways, and show that lateral redistribution of the protein into rafts is important for subsequent signal transduction.Received 22 July 2004; received after revision 10 September 2004; accepted 7 October 2004     

Differential stimulation of signaling pathways initiated by Edg-2 in response to lysophosphatidic acid or sphingosine-1-phosphate

Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are produced during cell activation and have multiple effects on cells. A family of seven transmembrane-spanning domain G-protein-coupled receptors, named Edg, mediate these effects of LPA and S1P. In this study, transient overexpression of Edg-2 sensitized MG63 human osteosarcoma cells to both LPA- and S1P-mediated stimulation of fibronectin matrix deposition and actin stress fiber formation. Both lipids were active in the 1-20 nM concentration range on cells transfected with Edg-2 as compared to the 10-200 nM range on mock-transfected cells. The signaling pathway for matrix deposition by Edg-2-transfected cells was Rho dependent. Overexpression of Edg-2 also caused a tenfold decrease in the concentration of either LPA or S1P that activated MAPKinase (Erkl/2) in MG63 cells. LPA- or S1P-stimulated activation of Erkl/2 was Gi dependent. These results indicate that, in MG63 cells, Edg-2 mediates actin stress fiber formation, fibronectin matrix assembly, and MAPKinase activation in response to either LPA or S1P.     

Immunological response between protozoa symbiotic to a roach and a termite

Résumé L'analyse des responsabilités immunologiques après immunisation d'animaux expérimentaux avec les protozoaires symbiotiques du roach,Cryptocercus et du termiteZootermopsis indique une étroite affinité chimique entre les protozoas de ces hôtes. Les résultats semblent confirmer indirectement la taxonomic morphologique courante des hôtes.