Proteomic Characterization of Cytoplasmic Lipid Droplets in Human Metastatic Breast Cancer Cells

Abstract

One of the characteristic features of metastatic breast cancer is increased cellular storage of neutral lipid in cytoplasmic lipid droplets (CLDs). CLD accumulation is associated with increased cancer aggressiveness, suggesting CLDs contribute to metastasis. However, how CLDs contribute to metastasis is not clear. CLDs are composed of a neutral lipid core, a phospholipid monolayer, and associated proteins. Proteins that associate with CLDs regulate both cellular and CLD metabolism; however, the proteome of CLDs in metastatic breast cancer and how these proteins may contribute to breast cancer progression is unknown. Therefore, the purpose of this study was to identify the proteome and assess the characteristics of CLDs in the MCF10CA1a human metastatic breast cancer cell line. Utilizing shotgun proteomics, we identified over 1500 proteins involved in a variety of cellular processes in the isolated CLD fraction. Interestingly, unlike other cell lines such as adipocytes or enterocytes, the most enriched protein categories were involved in cellular processes outside of lipid metabolism. For example, cell-cell adhesion was the most enriched category of proteins identified, and many of these proteins have been implicated in breast cancer metastasis. In addition, we characterized CLD size and area in MCF10CA1a cells using transmission electron microscopy. Our results provide a hypothesis-generating list of potential players in breast cancer progression and offers a new perspective on the role of CLDs in cancer.

A proximity labeling strategy enables proteomic analysis of inter-organelle membrane contacts

“…SQLE is an ER-resident protein and has been demonstrated as a component of LDs, and overexpression of SQLE leads to increased lipid accumulation in the mouse liver. 30 , 31 However, its role in inter-organelle interactions has not been addressed.…”

The Janus-Faced Role of Lipid Droplets in Aging: Insights from the Cellular Perspective

“…The affinity of this V-domain is higher for LDs than for mitochondria and, upon an increase in the cytosolic LD content (as seen in tumor cells), these apoptotic proteins are cleared from the mitochondria, with the relocalization to LDs interrupting the apoptotic program [ 35 ]. In fact, both pro- and anti-apoptotic proteins such as BAX [ 12 , 35 , 492 ], BCL-X L [ 35 ], Bcl-w [ 12 ], AIFM1, AIFM2 [ 12 ], CCAR2 [ 12 ], API5 [ 492 ], and TPT1 [ 35 , 492 ] were shown to localize to LDs in tumor cells.…”

A positive feedback loop between ZEB2 and ACSL4 regulates lipid metabolism to promote breast cancer metastasis

“…For lipid anabolism, FAs are stored in a dynamic organelle called a lipid droplet (LD), which is composed of a monolayer of phospholipids that covers a hydrophobic core containing neutral lipids, such as triacylglycerol (TAG) and cholesterol esterase (CE) ( Cruz et al, 2020 ). lipid droplets (LDs) accumulation is associated with aggressiveness in many cancer types ( Antunes et al, 2022 ), including breast ( Zembroski et al, 2021 ), brain ( Taïb et al, 2019 ), liver ( Niu et al, 2021 ), lung ( Jin and Yuan, 2020 ), and prostate ( Roman et al, 2020 ; Huang et al, 2012 ). Indeed, the aggregation of FAs in LDs is considered a priming state to prepare for metastasis ( Petan, 2020 ; Rozeveld et al, 2020 ; Senga et al, 2018 ).…”