TY  - JOUR
A1  - Bär, Ludmilla
A1  - Feger, Martina
A1  - Fajol, Abul
A1  - Klotz, Lars-Oliver
A1  - Zeng, Shufei
A1  - Lang, Florian
A1  - Hocher, Berthold
A1  - Föller, Michael
T1  - Insulin suppresses the production of fibroblast growth factor 23 (FGF23)
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Fibroblast growth factor 23 (FGF23) is produced by bone cells and regulates renal phosphate and vitamin D metabolism, as well as causing left ventricular hypertrophy. FGF23 deficiency results in rapid aging, whereas high plasma FGF23 levels are found in several disorders, including kidney or cardiovascular diseases. Regulators of FGF23 production include parathyroid hormone (PTH), calcitriol, dietary phosphate, and inflammation. We report that insulin and insulin-like growth factor 1 (IGF1) are negative regulators of FGF23 production. In UMR106 osteoblast-like cells, insulin and IGF1 down-regulated FGF23 production by inhibiting the transcription factor forkhead box protein O1 (FOXO1) through phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB)/Akt signaling. Insulin deficiency caused a surge in the serum FGF23 concentration in mice, which was reversed by administration of insulin. In women, a highly significant negative correlation between FGF23 plasma concentration and increase in plasma insulin level following an oral glucose load was found. Our results provide strong evidence that insulin/IGF1dependent PI3K/PKB/Akt/FOXO1 signaling is a powerful suppressor of FGF23 production in vitro as well as in mice and in humans.
KW  - PI3K
KW  - PKB/Akt
KW  - Klotho
KW  - phosphate
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1800160115
SN  - 0027-8424
VL  - 115
IS  - 22
SP  - 5804
EP  - 5809
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Gerhardt, Matthias
A1  - Walz, Michael
A1  - Beta, Carsten
T1  - Signaling in chemotactic amoebae remains spatially confined to stimulated membrane regions
JF  - Journal of cell science
N2  - Recent work has demonstrated that the receptor-mediated signaling system in chemotactic amoeboid cells shows typical properties of an excitable system. Here, we delivered spatially confined stimuli of the chemoattractant cAMP to the membrane of differentiated Dictyostelium discoideum cells to investigate whether localized receptor stimuli can induce the spreading of excitable waves in the G-protein-dependent signal transduction system. By imaging the spatiotemporal dynamics of fluorescent markers for phosphatidylinositol (3,4,5)-trisphosphate (PIP3), PTEN and filamentous actin, we observed that the activity of the signaling pathway remained spatially confined to the stimulated membrane region. Neighboring parts of the membrane were not excited and no receptor-initiated spatial spreading of excitation waves was observed. To generate localized cAMP stimuli, either particles that carried covalently bound cAMP molecules on their surface were brought into contact with the cell or a patch of the cell membrane was aspirated into a glass micropipette to shield this patch against freely diffusing cAMP molecules in the surrounding medium. Additionally, the binding site of the cAMP receptor was probed with different surface-immobilized cAMP molecules, confirming results from earlier ligand-binding studies.
KW  - Signal transduction
KW  - Excitable dynamics
KW  - Dictyostelium
KW  - cAMP
KW  - PIP3
KW  - PIP2
KW  - PI3K
KW  - PTEN
KW  - Micropipette aspiration
KW  - cAMP receptor
KW  - Patch clamp
Y1  - 2014
U6  - https://doi.org/10.1242/jcs.161133
SN  - 0021-9533
SN  - 1477-9137
VL  - 127
IS  - 23
SP  - 5115
EP  - 5125
PB  - Company of Biologists Limited
CY  - Cambridge
ER  -