Calpain-mediated cleavage generates a ZBTB18 N-terminal product that regulates HIF1A signaling and glioblastoma metabolism

Anie P Masilamani; Rana Schulzki; Shuai Yuan; Ira V Haase; Eva Kling; Franziska Dewes; Geoffroy Andrieux; Melanie Börries; Oliver Schnell; Dieter H Heiland; Oliver Schilling; Roberto Ferrarese; Maria S Carro

doi:10.1016/j.isci.2022.104625

Calpain-mediated cleavage generates a ZBTB18 N-terminal product that regulates HIF1A signaling and glioblastoma metabolism

iScience. 2022 Jun 17;25(7):104625. doi: 10.1016/j.isci.2022.104625. eCollection 2022 Jul 15.

Authors

Anie P Masilamani¹, Rana Schulzki¹, Shuai Yuan¹, Ira V Haase¹, Eva Kling¹, Franziska Dewes¹, Geoffroy Andrieux^{2

3}, Melanie Börries^{2

3}, Oliver Schnell¹, Dieter H Heiland^{1

3}, Oliver Schilling^{3

4}, Roberto Ferrarese¹, Maria S Carro¹

Affiliations

¹ Department of Neurosurgery, Medical Center - University of Freiburg, Freiburg, Germany.
² Institute of Medical Bioinformatics and Systems Medicine, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
³ German Cancer Consortium (DKTK) and German Cancer Research Center (DKFZ), Partner Site Freiburg, Freiburg, Germany.
⁴ Institute of Clinical Pathology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.

Abstract

Proteolytic cleavage is an important post-translational mechanism to increase protein variability and functionality. In cancer, this process can be deregulated to shut off tumor-suppressive functions. Here, we report that in glioblastoma (GBM), the tumor suppressor ZBTB18 is targeted for protein cleavage by the intracellular protease calpain. The N-terminal (Nte) ZBTB18 cleaved fragment localizes to the cytoplasm and thus, is unable to exert the gene expression repressive function of the uncleaved protein. Mass spectrometry (MS) analysis indicates that the Nte ZBTB18 short form (SF) interacts with C-terminal (Cte) binding proteins 1 and 2 (CTBP1/2), which appear to be involved in HIF1A signaling activation. In fact, we show that the new ZBTB18 product activates HIF1A-regulated genes, which in turn lead to increased lipid uptake, lipid droplets (LD) accumulation, and enhanced metabolic activity. We propose that calpain-mediated ZBTB18 cleavage represents a new mechanism to counteract ZBTB18 tumor suppression and increase tumor-promoting functions in GBM cells.

Keywords: Biochemistry; Cancer; Molecular biology; Transcriptomics.