Restoration of Compact Golgi Morphology in Advanced Prostate Cancer Enhances Susceptibility to Galectin-1–Induced Apoptosis by Modifying Mucin O-Glycan Synthesis

Abstract

Prostate cancer progression is associated with up-regulation of sialyl-T antigen produced by β-galactoside α-2,3-sialyltransferase-1 (ST3Gal1) but not with core 2-associated polylactosamine despite expression of core 2 N-acetylglucosaminyltransferase-L (C2GnT-L/GCNT1). This property allows androgen-refractory prostate cancer cells to evade galectin-1 (LGALS1)-induced apoptosis, but the mechanism is not known. We have recently reported that Golgi targeting of glycosyltransferases is mediated by golgins: giantin (GOLGB1) for C2GnT-M (GCNT3) and GM130 (GOLGA2)-GRASP65 (GORASP1) or GM130-giantin for core 1 synthase. Here, we show that for Golgi targeting, C2GnT-L also uses giantin exclusively while ST3Gal1 employs either giantin or GM130-GRASP65. In addition, the compact Golgi morphology is detected in both androgen-sensitive prostate cancer and normal prostate cells, but fragmented Golgi and mislocalization of C2GnT-L are found in androgen-refractory cells as well as primary prostate tumors (Gleason grade 2–4). Furthermore, failure of giantin monomers to be phosphorylated and dimerized prevents Golgi from forming compact morphology and C2GnT-L from targeting the Golgi. On the other hand, ST3Gal1 reaches the Golgi by an alternate site, GM130-GRASP65. Interestingly, inhibition or knockdown of non-muscle myosin IIA (MYH9) motor protein frees up Rab6a GTPase to promote phosphorylation of giantin by polo-like kinase 3 (PLK3), which is followed by dimerization of giantin assisted by protein disulfide isomerase A3 (PDIA3), and restoration of compact Golgi morphology and targeting of C2GnT-L. Finally, the Golgi relocation of C2GnT-L in androgen-refractory cells results in their increased susceptibility to galectin-1-induced apoptosis by replacing sialyl-T antigen with polylactosamine.

Golgb1 regulates protein glycosylation and is crucial for mammalian palate development

“…2G,H). These data are consistent with previous reports from Golgb1 (giantin) knockdown studies in tissue culture cells showing that Golgb1 is not required for Golgi structural integrity (Petrosyan et al, 2012(Petrosyan et al, , 2014Puthenveedu and Linstedt, 2001;Wong and Munro, 2014).…”

“…In particular, siRNA knockdown studies suggest that the C2GnT-M and C2GnT-L synthases in the O-glycosylation pathway use Golgb1 exclusively to target to Golgi membrane, whereas C1GalT1 and ST3Gal1 synthases use Golgb1 and GM130-Grasp65 (also known as Gorasp1) as alternative docking sites (Petrosyan et al, 2012(Petrosyan et al, , 2014Wong and Munro, 2014). O-glycosylation in the Golgi starts with synthesis of the glycoconjugate GalNAc-α1-O-Ser/Thr, known as the Tn antigen.…”

Keratin 1 Plays a Critical Role in Golgi Localization of Core 2 N-Acetylglucosaminyltransferase M via Interaction with Its Cytoplasmic Tail

“…In this study we examined the effect of the presence or absence of KRT1 on the appearance of T-antigen as detected by PNA lectin staining. The presence of C2GnT-M in the Golgi, which is KRT1-dependent, is expected to prevent the masking of the T-antigen with ␣2-3Sia (␣2,3-linked sialic acid) by out-competing ST3Gal1 for the T-antigen (22,59) (Fig. 6A).…”

“…This study also demonstrated that Giantin, GM130-GRASP65, and GM130-Giantin are the Golgi targeting sites for GTs in a GT-specific manner. Recently, we also show that in advanced prostate cancer cells, differential Golgi targeting of Gal␤1-3GalNAc␣Ser/Thr:␣2-3-sialyltransferase 1 (ST3Gal1) and core 2 N-acetylglucosaminyltransferase-L/1 (C2GnT-L) determines the susceptibility of these cells to Galectin-1-induced apoptosis (22).…”

“…However, other reports show that this process is COPI-independent (11, 28 -30). We have shown that this step is mediated by non-muscle myosin IIA (NMIIA) (30), and the interaction of the C-terminal cargo binding region of NMIIA with the CT of GTs is responsible for not only the recycling of GTs and the remodeling of the Golgi under normal physiological conditions but also Golgi fragmentation in stressed cells (19,20) and advanced cancer cells (22).…”