Flotillin-1 palmitoylation is essential for its stability and subsequent tumor promoting capabilities.

Andrew J Brenner, Christopher A Jolly, Bryan McClellan, Crystal N Wilson, Linda deGraffenried

Journal: Oncogene 2024;43(14):1063-1074

PMID: 38374406

Full Text on Nature Publishing Group View on PubMed

Abstract

Flotillin-1 contributes to invasion and metastasis in triple negative breast cancer (TNBC) and is modified post-translationally through palmitoylation. Palmitoylation, the process of conjugating palmitoyl-CoA to proteins, plays an essential role in protein stability and trafficking. Thus far, there has not been any investigation into the role of flotillin-1 palmitoylation in the context of metastasis in vivo. To address the role of flotillin-1 palmitoylation in metastasis, MDA-MB-231 cells expressing palmitoylation defective flotillin-1 constructs were used as models. Compared to flotillin-1 WT expressing tumors, flotillin-1 palmitoylation defective displayed abrogated tumor progression and lung metastasis in vivo in both spontaneous and experimental models. Further mechanistic investigation led to the identification of zDHHC5 as the main palmitoyl acyltransferase responsible for palmitoylating endogenous flotillin-1. Modulation of flotillin-1 palmitoylation status through mutagenesis, zDHHC5 silencing, and 2-bromopalmitate inhibition all resulted in the proteasomal degradation of flotillin-1 protein. To assess if flotillin-1 palmitoylation can be inhibited for potential clinical relevance, we designed a competitive peptide fused to a cell penetrating peptide sequence, which displayed efficacy in blocking flotillin-1 palmitoylation in vitro without altering palmitoylation of other zDHHC5 substrates, highlighting its specificity. Additionally, TNBC xenograft tumor models expressing a doxycycline inducible flotillin-1 palmitoylation inhibiting peptide displayed attenuated tumor growth and lung metastasis. Collectively, these results reveal a novel palmitoylation dependent mechanism which is essential for the stability of flotillin-1 protein. More specifically, disruption of flotillin-1 palmitoylation through mutagenesis or competitive peptide promoted flotillin-1 protein degradation, subsequently impeding its tumor promoting and metastasis-inducing effects in TNBC tumor models.

Address: Department of Nutritional Sciences, The University of Texas at Austin, Austin, TX, USA.; Department of Nutritional Sciences, The University of Texas at Austin, Austin, TX, USA.; Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, USA.; Mays Cancer Center, University of Texas Health Science Center, San Antonio, TX, USA.; Division of Hematology and Oncology, Department of Medicine, University of Texas Health Science Center, San Antonio, TX, USA.; Department of Nutritional Sciences, The University of Texas at Austin, Austin, TX, USA.; Mays Cancer Center, University of Texas Health Science Center, San Antonio, TX, USA.; Department of Nutritional Sciences, The University of Texas at Austin, Austin, TX, USA. [email protected].; Mays Cancer Center, University of Texas Health Science Center, San Antonio, TX, USA. [email protected].

DOI: 10.1038/s41388-024-02946-0