TY  - JOUR
A1  - Bisti, F.
A1  - Rogalev, V. A.
A1  - Karolak, M.
A1  - Paul, S.
A1  - Gupta, A.
A1  - Schmitt, T.
A1  - Güntherodt, G.
A1  - Eyert, V.
A1  - Sangiovanni, G.
A1  - Profeta, G.
A1  - Strocov, V. N.
T1  - Weakly-correlated nature of ferromagnetism in nonsymmorphic CrO\(_2\) revealed by bulk-sensitive soft-X-ray ARPES
JF  - Physical Review X
N2  - Chromium dioxide CrO\(_2\) belongs to a class of materials called ferromagnetic half-metals, whose peculiar aspect is that they act as a metal in one spin orientation and as a semiconductor or insulator in the opposite one. Despite numerous experimental and theoretical studies motivated by technologically important applications of this material in spintronics, its fundamental properties such as momentumresolved electron dispersions and the Fermi surface have so far remained experimentally inaccessible because of metastability of its surface, which instantly reduces to amorphous Cr\(_2\)O\(_3\). In this work, we demonstrate that direct access to the native electronic structure of CrO\(_2\) can be achieved with soft-x-ray angle-resolved photoemission spectroscopy whose large probing depth penetrates through the Cr\(_2\)O\(_3\) layer. For the first time, the electronic dispersions and Fermi surface of CrO\(_2\) are measured, which are fundamental prerequisites to solve the long debate on the nature of electronic correlations in this material. Since density functional theory augmented by a relatively weak local Coulomb repulsion gives an exhaustive description of our spectroscopic data, we rule out strong-coupling theories of CrO\(_2\). Crucial for the correct interpretation of our experimental data in terms of the valence-band dispersions is the understanding of a nontrivial spectral response of CrO\(_2\) caused by interference effects in the photoemission process originating from the nonsymmorphic space group of the rutile crystal structure of CrO\(_2\).
KW  - physics
KW  - electronic structure
KW  - half-metals
KW  - angle-resolved photoemission spectroscopy
KW  - band structure methods
KW  - DFT+U
KW  - condensed matter physics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172251
VL  - 7
IS  - 4
ER  - 
TY  - JOUR
A1  - Schmitt, T.
A1  - Egu, D.T.
A1  - Walter, E.
A1  - Sigmund, A.M.
A1  - Eichkorn, R.
A1  - Yazdi, A.
A1  - Schmidt, E.
A1  - Sárdy, M.
A1  - Eming, R.
A1  - Goebeler, M.
A1  - Waschke, J.
T1  - Ca\(^{2+}\) signalling is critical for autoantibody‐induced blistering of human epidermis in pemphigus
JF  - British Journal of Dermatology
N2  - Background
Pemphigus is a severe bullous autoimmune skin disease. Pemphigus foliaceus (PF) is characterized by antidesmoglein (Dsg) 1 IgG causing epidermal blistering; mucosal pemphigus vulgaris (mPV) by anti‐Dsg3 IgG inducing erosions in the mucosa; and mucocutaneous pemphigus vulgaris (PV) by affecting both, with autoantibodies targeting Dsg1 and Dsg3.
Objectives
To characterize the Ca\(^{2+}\) flux pathway and delineate its importance in pemphigus pathogenesis and clinical phenotypes caused by different antibody profiles.
Methods
Immunoprecipitation, Ca\(^{2+}\) flux analysis, Western blotting, immunofluorescence staining, dissociation assays and a human skin ex vivo model were used.
Results
PV IgG and PF IgG, but neither Dsg3‐specific monoclonal antibody (AK23) nor mPV IgG, caused Ca\(^{2+}\) influx in primary human keratinocytes. Phosphatidylinositol 4‐kinase α interacts with Dsg1 but not with Dsg3. Its downstream target – phospholipase‐C‐γ1 (PLC) – was activated by PV IgG and PF IgG but not AK23 or mPV IgG. PLC releases inositol 1,4,5‐trisphosphate (IP3) causing IP3 receptor (IP3R) activation and Ca2+ flux from the endoplasmic reticulum into the cytosol, which stimulates Ca2+ release‐activated channels (CRAC)‐mediated Ca\(^{2+}\) influx. Inhibitors against PLC, IP3R and CRAC effectively blocked PV IgG and PF IgG‐induced Ca\(^{2+}\) influx; ameliorated alterations of Dsg1 and Dsg3 localization, and reorganization of keratin and actin filaments; and inhibited loss of cell adhesion in vitro. Finally, inhibiting PLC or IP3R was protective against PV IgG‐induced blister formation and redistribution of Dsg1 and Dsg3 in human skin ex vivo.
Conclusions
Ca2+‐mediated signalling is important for epidermal blistering and dependent on the autoantibody profile, which indicates different roles for signalling complexes organized by Dsg1 and Dsg3. Interfering with PLC and Ca\(^{2+}\) signalling may be a promising approach to treat epidermal manifestations of pemphigus.
KW  - pemphigus
KW  - epidermis
KW  - Ca\(^{2+}\) signalling
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-262810
VL  - 185
IS  - 3
SP  - 595
EP  - 604
ER  -