PubMed Health⌕ Search

Biomedical subjects

T Jahn

Publications and source records attributed to T Jahn.

24 records · Page 2Linked to original sources
PubMed1997

The 14-3-3 protein interacts directly with the C-terminal region of the plant plasma membrane H(+)-ATPase.

Accumulating evidence suggests that 14-3-3 proteins are involved in the regulation of plant plasma membrane H(+)-ATPase activity. However, it is not known whether the 14-3-3 protein interacts directly or indirectly with the H(+)-ATPase. In this study, detergent-solubilized plasma membrane H(+)-ATPase isolated from fusicoccin-treated maize shoots was copurified with the 14-3-3 protein (as determined by protein gel blotting), and the H(+)-ATPase was recovered in an activated state. In the absence of fusicoccin treatment, H(+)-ATPase and the 14-3-3 protein were well separated, and the H(+)-ATPase was recovered in a nonactivated form. Trypsin treatment removed the 10-kD C-terminal region from the H(+)-ATPase as well as the 14-3-3 protein. Using the yeast two-hybrid system, we could show a direct interaction between Arabidopsis 14-3-3 GF14-phi and the last 98 C-terminal amino acids of the Arabidopsis AHA2 plasma membrane H(+)-ATPase. We propose that the 14-3-3 protein is a natural ligand of the plasma membrane H(+)-ATPase, regulating proton pumping by displacing the C-terminal autoinhibitory domain of the H(+)-ATPase.

14-3-3 Proteins↗
PubMed1996

Reconstitution of T cell receptor signaling in ZAP-70-deficient cells by retroviral transduction of the ZAP-70 gene.

A variant of severe combined immunodeficiency syndrome (SCID) with a selective inability to produce CD8 single positive T cells and a signal transduction defect in peripheral CD4+ cells has recently been shown to be the result of mutations in the ZAP-70 gene. T cell receptor (TCR) signaling requires the association of the ZAP-70 protein tyrosine kinase with the TCR complex. Human T cell leukemia virus type I-transformed CD4+ T cell lines were established from ZAP-70-deficient patients and normal controls. ZAP-70 was expressed and appropriately phosphorylated in normal T cell lines after TCR engagement, but was not detected in T cell lines from ZAP-70-deficient patients. To determine whether signaling could be reconstituted, wild-type ZAP-70 was introduced into deficient cells with a ZAP-70 retroviral vector. High titer producer clones expressing ZAP-70 were generated in the Gibbon ape leukemia virus packaging line PG13. After transduction, ZAP-70 was detected at levels equivalent to those observed in normal cells, and was appropriately phosphorylated on tyrosine after receptor engagement. The kinase activity of ZAP-70 in the reconstituted cells was also appropriately upregulated by receptor aggregation. Moreover, normal and transduced cells, but not ZAP-70-deficient cells, were able to mobilize calcium after receptor ligation, indicating that proximal TCR signaling was reconstituted. These results indicate that this form of SCID may be corrected by gene therapy.

CD4-Positive T-Lymphocytes↗
PubMed1996

Correction of interleukin-2 receptor function in X-SCID lymphoblastoid cells by retrovirally mediated transfer of the gamma-c gene.

X-SCID, the most common form of human SCID, is due to mutations in the common gamma chain gene (gamma-c) that encodes an essential component of the cytokine receptors for interleukin-2 (IL-2), IL-4, IL-7, IL-9, and IL-15. Activation of the Janus family tyrosine kinases Jak1 and Jak3 is necessary for appropriate signalling through the IL-2 receptor (IL-2R). Neither Jak1 nor Jak3 was phosphorylated after IL-2 stimulation of an Epstein-Barr virus-transformed cell line (LCL) from an X-SCID patient with a gamma-c null mutation. However, we now show that appropriate IL-2R function can be restored in an X-SCID LCL by transduction of a wild-type gamma-c gene. A retroviral vector, G1gamma-cSvNa, was constructed and produced in the PG13 packaging line. Transduced X-SCID LCL expressed the G1gamma-cSvNa transcript. IL-2 stimulation of the transduced cell line resulted in appropriate tyrosine phosphorylation of both Jak1 and Jak3. Thus, retroviral-mediated transduction of normal gamma-c can reconstitute downstream signalling through the IL-2R in X-SCID cell lines, suggesting that gene therapy may be a treatment for this disease.

B-Lymphocytes↗
PubMed1996

Monitoring of task performance during functional magnetic resonance imaging of sensorimotor cortex at 1.5 T.

Functional magnetic resonance imaging (fMRI) has found widespread clinical interest. Difficulties in clinical use of the fMRI technique arise, considering the lack of knowledge about activation task performance. This accounts especially for sensorimotor activation studies, in which performance of the sensorimotor activation task is-if at all-usually rated visually by subjective or semiquantitative methods (i.e., defining categories of performance such as neurological soft signs scales). Recently, instrumental methods for the measurement and analysis of motor performance have been developed. Pronation/supination (hand rotation) movement was shown to be an easily measurable and promising motor task. We have adapted a mechanic device (pronation/supination device, PSD) to monitor motor performance during the fMRI experiment. In a feasibility study, an investigation of fMRI activation strength dependence of sensorimotor cortices and supplementary motor area upon task frequency (25, 50, and 75 cycles/min) was carried out on 10 right-handed healthy volunteers. Furthermore, the authors report the observation of stimulus-induced activation changes in the cerebellum during pronation/supination movement.

Hand↗
PubMed1993

Relationship between crossover and modality shift effects in sequential reaction time performance of schizophrenic patients.

On the basis of reaction time measurement, two well-known experimental indicators of attentional dysfunctions in schizophrenia were studied. These are the crossover effect (COE), induced by alternating preparatory intervals, and the modality shift effect (MSE), induced by alternating stimulus modalities. For the first time, the relationship between these indicators was examined. Correlations of both indicators with clinical variables such as psychopathology, subjective complaints, duration of illness and medication were also analyzed. Subjects were 50 schizophrenic inpatients and 50 healthy controls, 21 women and 29 men in each group. While earlier results for COE and MSE were replicable, no correlation between the two was found, leading to the conclusion that they involve different aspects of attention not necessarily impaired to the same extent in all patients.

Adolescent↗