TFG is required for autophagy flux and to prevent endoplasmic reticulum stress in CH12 B lymphoma cells

Steinmetz T, Schlötzer-Schrehardt U, Hearne A, Schuh W, Wittner J, Schulz S, Winkler T, Jäck HM, Mielenz D (2020)

Publication Type: Journal article

Publication year: 2020

Journal

Autophagy Taylor & Francis

DOI: 10.1080/15548627.2020.1821546

Abstract

Plasma cells depend on quality control of newly synthesized antibodies in the endoplasmic reticulum (ER) via macroautophagy/autophagy and proteasomal degradation. The cytosolic adaptor protein TFG (Trk-fused gene) regulates ER-Golgi transport, the secretory pathway and proteasome activity in non-immune cells. We show here that TFG is upregulated during lipopolysaccharide- and CpG-induced differentiation of B1 and B2 B cells into plasmablasts, with the highest expression of TFG in mature plasma cells. CRISPR-CAS9-mediated gene disruption of tfg in the B lymphoma cell line CH12 revealed increased apoptosis, which was reverted by BCL2 but even more by ectopic TFG expression. Loss of TFG disrupted ER structure, leading to an expanded ER and increased expression of ER stress genes. When compared to wild-type CH12 cells, tfg KO CH12 cells were more sensitive toward ER stress induced by tunicamycin, monensin and proteasome inhibition or by expression of an ER-bound immunoglobulin (Ig) μ heavy (µH) chain. CH12 tfg KO B cells displayed more total LC3, lower LC3-II turnover and increased numbers and size of autophagosomes. Tandem-fluorescent-LC3 revealed less accumulation of GFP-LC3 in starved and chloroquine-treated CH12 tfg KO B cells. The GFP:RFP ratio of tandem-fluorescent-LC3 was higher in tunicamycin-treated CH12 tfg KO B cells, suggesting less autophagy flux during induced ER stress. Based on these data, we suggest that TFG controls autophagy flux in CH12 B cells and propose that TFG is a survival factor that alleviates ER stress through the support of autophagy flux in activated B cells and mature plasma cells.

Authors with CRIS profile

Tobit Steinmetz Professur für Immunologie Ursula Schlötzer-Schrehardt Medizinische Fakultät Wolfgang Schuh Department of Molecular Immunology Jens Wittner Department of Molecular Immunology Sebastian Schulz Professur für Immunologie Thomas Winkler Professur für Genetik Hans-Martin Jäck Department of Molecular Immunology Dirk Mielenz Medizinische Fakultät

How to cite

APA:

Steinmetz, T., Schlötzer-Schrehardt, U., Hearne, A., Schuh, W., Wittner, J., Schulz, S.,... Mielenz, D. (2020). TFG is required for autophagy flux and to prevent endoplasmic reticulum stress in CH12 B lymphoma cells. Autophagy. https://doi.org/10.1080/15548627.2020.1821546

MLA:

Steinmetz, Tobit, et al. "TFG is required for autophagy flux and to prevent endoplasmic reticulum stress in CH12 B lymphoma cells." Autophagy (2020).

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