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Updated: Jul 26, 2025
Quantitative Analysis of Autophagy using Advanced 3D Fluorescence Microscopy
Published on: May 3, 2013
Targeting the ATF6-Mediated ER Stress Response and Autophagy Blocks Integrin-Driven Prostate Cancer Progression
Amanda J Macke1,2, Artem N Pachikov1,2, Taylor E Divita1,2
1Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska.
Abstract:
Prostate cancer progression to the lethal metastatic castration-resistant phenotype (mCRPC) is driven by αv integrins and is associated with Golgi disorganization and activation of the ATF6 branch of unfolded protein response (UPR). Overexpression of integrins requires N-acetylglucosaminyltransferase-V (MGAT5)-mediated glycosylation and subsequent cluster formation with Galectin-3 (Gal-3). However, the mechanism underlying this altered glycosylation is missing. For the first time, using HALO analysis of IHC, we found a strong association of integrin αv and Gal-3 at the plasma membrane (PM) in primary prostate cancer and mCRPC samples. We discovered that MGAT5 activation is caused by Golgi fragmentation and mislocalization of its competitor, N-acetylglucosaminyltransferase-III, MGAT3, from Golgi to the endoplasmic reticulum (ER). This was validated in an ethanol-induced model of ER stress, where alcohol treatment in androgen-refractory PC-3 and DU145 cells or alcohol consumption in patient with prostate cancer samples aggravates Golgi scattering, activates MGAT5, and enhances integrin expression at PM. This explains known link between alcohol consumption and prostate cancer mortality. ATF6 depletion significantly blocks UPR and reduces the number of Golgi fragments in both PC-3 and DU145 cells. Inhibition of autophagy by hydroxychloroquine (HCQ) restores compact Golgi, rescues MGAT3 intra-Golgi localization, blocks glycan modification via MGAT5, and abrogates delivery of Gal-3 to the cell surface. Importantly, the loss of Gal-3 leads to reduced integrins at PM and their accelerated internalization. ATF6 depletion and HCQ treatment synergistically decrease integrin αv and Gal-3 expression and temper orthotopic tumor growth and metastasis.
Implications:
Combined ablation of ATF6 and autophagy can serve as new mCRPC therapeutic.
Insights
Metastatic castration-resistant prostate cancer (mCRPC) progression involves altered glycosylation and Golgi disorganization. Inhibiting ATF6 and autophagy simultaneously reduces integrin expression and tumor growth, offering a potential mCRPC therapy.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Prostate cancer progresses to lethal metastatic castration-resistant prostate cancer (mCRPC) driven by αv integrins.
- This progression is linked to Golgi disorganization and activation of the ATF6 branch of the unfolded protein response (UPR).
- Altered glycosylation, specifically N-acetylglucosaminyltransferase-V (MGAT5)-mediated, and Galectin-3 (Gal-3) clustering are implicated in integrin overexpression, but the underlying mechanism is unclear.
Purpose of the Study:
- To elucidate the mechanism linking Golgi disorganization, UPR activation, and altered glycosylation in prostate cancer progression.
- To investigate the role of MGAT5, MGAT3, and Gal-3 in integrin αv localization and function.
- To evaluate the therapeutic potential of targeting ATF6 and autophagy in mCRPC.
Main Methods:
- HALO analysis of immunohistochemistry (IHC) on primary and mCRPC samples.
- Ethanol-induced endoplasmic reticulum (ER) stress model in prostate cancer cell lines (PC-3, DU145).
- Assessment of Golgi morphology, protein localization (MGAT3, Gal-3), and integrin αv expression.
- Inhibition of ATF6 and autophagy (using hydroxychloroquine - HCQ) in cell lines and orthotopic tumor models.
Main Results:
- A strong association between integrin αv and Gal-3 at the plasma membrane (PM) was observed in prostate cancer samples.
- Golgi fragmentation and MGAT3 mislocalization to the ER were identified as causes of MGAT5 activation.
- Ethanol exposure exacerbated Golgi scattering, activated MGAT5, and increased PM integrin expression, linking alcohol consumption to prostate cancer mortality.
- ATF6 depletion reduced Golgi fragments and UPR.
- Autophagy inhibition (HCQ) restored Golgi structure, rescued MGAT3 localization, blocked MGAT5 activity, and reduced cell surface Gal-3.
- Loss of Gal-3 decreased PM integrins and increased their internalization.
- Combined ATF6 depletion and HCQ treatment synergistically reduced integrin αv and Gal-3, suppressed tumor growth, and decreased metastasis.
Conclusions:
- Golgi fragmentation and MGAT3 mislocalization drive MGAT5-mediated glycosylation and integrin overexpression in mCRPC.
- Alcohol consumption exacerbates these changes, contributing to prostate cancer mortality.
- Combined inhibition of ATF6 and autophagy presents a promising therapeutic strategy for mCRPC by reducing integrin signaling and tumor progression.
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