iScience
Volume 25, Issue 7, 15 July 2022, 104625
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Article
Calpain-mediated cleavage generates a ZBTB18 N-terminal product that regulates HIF1A signaling and glioblastoma metabolism

https://doi.org/10.1016/j.isci.2022.104625Get rights and content
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Highlights

  • Calpain mediates ZBTB18 cleavage in GBM cells

  • ZBTB18 SF-Nte localizes in the cytoplasm and interacts with CTBP1/2

  • ZBTB18 SF-Nte regulates the expression of HIF targets

  • ZBTB18 SF-Nte regulates lipid uptake

Summary

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.

Subject areas

Biochemistry
Molecular biology
Cancer
Transcriptomics

Data and code availability

  • Single-cell RNA-seq data have been deposited at GEO and are publicly available as of the date of publication. The protein interactions from this publication have been submitted to the IMEx (www.imexconsortium.org) consortium through IntAct. (Orchard et al., 2014). Accession numbers are listed in the key resources table. Original western blot images have been deposited at Mendeley and are publicly available as of the date of publication. The DOI is listed in the key resources table. Microscopy data reported in this paper will be shared by the lead contact upon request.

  • This paper does not report original code.

  • Any additional information required to reanalyze the data reported in this paper is available from the lead contact upon request.

Cited by (0)

5

Present address: School of Medicine, Henan Polytechnic University, Henan, China

6

These authors contributed equally

7

Lead contact