SLC9A3R1 stimulates autophagy via BECN1 stabilization in breast cancer cells

Abstract

Abbreviations: BCL2, B-cell CLL/lymphoma 2; CHX, cycloheximide; CQ, chloroquine; EGFR, epidermal growth factor receptor; MAP1LC3/LC3, microtubule-associated protein 1 light chain 3; MTOR, mechanistic target of rapamycin (serine/threonine kinase); PI3K, phosphatidylinositol-4,5-bisphosphate 3-kinase; PIK3C3, phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4, phosphoinositide-3-kinase regulatory subunit 4; PTEN, phosphatase and tensin homolog; SLC9A3R1, solute carrier family 9, subfamily A (NHE3, cation proton antiporter 3), member 3 regulator 1; UB, ubiquitin.Autophagy, a self-catabolic process, has been found to be involved in abrogating the proliferation and metastasis of breast cancer. SLC9A3R1 (solute carrier family 9, subfamily A [NHE3, cation proton antiporter 3], member 3 regulator 1), a multifunctional scaffold protein, is involved in suppressing breast cancer cells proliferation and the SLC9A3R1-related signaling pathway regulates the activation of autophagy processes. However, the precise regulatory mechanism and signaling pathway of SLC9A3R1 in the regulation of autophagy processes in breast cancer cells remains unknown. Here, we report that the stability of BECN1, the major component of the autophagic core lipid kinase complex, is augmented in SLC9A3R1-overexpressing breast cancer MDA-MB-231 cells, subsequently stimulating autophagy by attenuating the interaction between BECN1 and BCL2. Initially, we found that SLC9A3R1 partially stimulated autophagy through the PTEN-PI3K-AKT1 signaling cascade in MDA-MB-231 cells. SLC9A3R1 then attenuated the interaction between BECN1 and BCL2 to stimulate the autophagic core lipid kinase complex. Further findings revealed that SLC9A3R1 bound to BECN1 and subsequently blocked ubiquitin-dependent BECN1 degradation. And the deletion of the C-terminal domain of SLC9A3R1 resulted in significantly reduced binding to BECN1. Moreover, the lack of C-terminal of SLC9A3R1 neither reduced the ubiquitination of BECN1 nor induced autophagy in breast cancer cells. The decrease in BECN1 degradation induced by SLC9A3R1 resulted in the activity of autophagy stimulation in breast cancer cells. These findings indicate that the SLC9A3R1-BECN1 signaling pathway participates in the activation of autophagy processes in breast cancer cells.

SPHK1 (sphingosine kinase 1) induces epithelial-mesenchymal transition by promoting the autophagy-linked lysosomal degradation of CDH1/E-cadherin in hepatoma cells

“…3A and B). The conversion of the soluble form of MAP1LC3/LC3 (MAP1LC3-I) to a lipidated form (MAP1LC3-II) is a marker of autophagy, and SQSTM1/p62, a “cargo” protein, is recognized as a marker of autophagy flux 16 . SPHK1 overexpression increased the expression of MAP1LC3-II and decreased the level of SQSTM1 in HepG2 cells (Fig.…”

Melanoma proteomics unravels major differences related to mutational status

“…Potassium channel tetradimerization domain containing 12 (KCTD12) inhibits proliferation in uveal melanoma cells [23]. SLC9A3R1 is involved in suppressing breast cancer cells proliferation [24]. Annexin A6 (ANXA6) acts as a tumor suppressor in skin cancer and it is involved in in the conversion of melanocytes to malignant melanomas [25].…”

The anti‐hepatic fibrosis effects of dihydrotanshinone I are mediated by disrupting the yes‐associated protein and transcriptional enhancer factor D2 complex and stimulating autophagy

“…Cells were fixed in 4% formaldehyde for 15 min and then permeabilized with 0.5% Triton X‐100 for 30 min at room temperature. After incubation with a primary antibody at 4°C overnight and a fluorescent secondary antibody (Alexa Fluor‐488 anti‐rabbit antibody, Invitrogen) for 1 h at room temperature, the cells were imaged using a fluorescence microscope (OLYMPUS, IX73) (Liu et al , ).…”