Binding of the Sialic Acid-binding Lectin, Siglec-9, to the Membrane Mucin, MUC1, Induces Recruitment of β-Catenin and Subsequent Cell Growth

Shuhei Tanida,Kaoru Akita,Akiko Ishida,Yugo Mori,Munetoyo Toda,Mizue Inoue,Mariko Ohta,Masakazu Yashiro,Tetsuji Sawada,Kosei Hirakawa,Hiroshi Nakada

doi:10.1074/jbc.m113.471318

Shuhei Tanida, Kaoru Akita + Show 9 more

Open Access

https://doi.org/10.1074/jbc.m113.471318

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Abstract

Because MUC1 carries a variety of sialoglycans that are possibly recognized by the siglec family, we examined MUC1-binding siglecs and found that Siglec-9 prominently bound to MUC1. An immunochemical study showed that Siglec-9-positive immune cells were associated with MUC1-positive cells in human colon, pancreas, and breast tumor tissues. We investigated whether or not this interaction has any functional implications for MUC1-expressing cells. When mouse 3T3 fibroblast cells and a human colon cancer cell line, HCT116, stably transfected with MUC1cDNA were ligated with recombinant soluble Siglec-9, β-catenin was recruited to the MUC1 C-terminal domain, which was enhanced on stimulation with soluble Siglec-9 in dose- and time-dependent manners. A co-culture model of MUC1-expressing cells and Siglec-9-expressing cells mimicking the interaction between MUC1-expressing malignant cells, and Siglec-9-expressing immune cells in a tumor microenvironment was designed. Brief co-incubation of Siglec-9-expressing HEK293 cells, but not mock HEK293 cells, with MUC1-expressing cells similarly enhanced the recruitment of β-catenin to the MUC1 C-terminal domain. In addition, treatment of MUC1-expressing cells with neuraminidase almost completely abolished the effect of Siglec-9 on MUC1-mediated signaling. The recruited β-catenin was thereafter transported to the nucleus, leading to cell growth. These findings suggest that Siglec-9 expressed on immune cells may play a role as a potential counterreceptor for MUC1 and that this signaling may be another MUC1-mediated pathway and function in parallel with a growth factor-dependent pathway.

Highlights

MUC1 plays a role in mediation of signaling initiated by growth factors
When mouse 3T3 fibroblast cells and a human colon cancer cell line, HCT116, stably transfected with MUC1cDNA were ligated with recombinant soluble Siglec-9, ␤-catenin was recruited to the MUC1 C-terminal domain, which was enhanced on stimulation with soluble Siglec-9 in dose- and time-dependent manners
Cells—Mouse fibroblast NIH3T3 cells, a human colon cancer cell line, HCT116, a human embryonic kidney cell line, HEK293, and a human alveolar cell line, A549, were obtained from the American Type Culture Collection. 3T3/MUC1 and HCT116/MUC1 cells were prepared by introducing MUC1cDNA into mouse 3T3 fibroblasts and human colon cancer HCT116 cells, respectively, as described previously [9], and 3T3 and HCT116 mock cells were prepared by transfection of the empty vector. 3T3/mock and 3T3/MUC1 cells were cultured in RPMI 1640 medium containing 2 mM L-glutamine and 10% fetal calf serum

Summary

Introduction

Results: Siglec-9-positive cells are associated with MUC1-positive tumor cells in tumor tissues, and Siglec-9 binds to MUC1. An immunochemical study showed that Siglec-9-positive immune cells were associated with MUC1-positive cells in human colon, pancreas, and breast tumor tissues. When mouse 3T3 fibroblast cells and a human colon cancer cell line, HCT116, stably transfected with MUC1cDNA were ligated with recombinant soluble Siglec-9, ␤-catenin was recruited to the MUC1 C-terminal domain, which was enhanced on stimulation with soluble Siglec-9 in dose- and time-dependent manners. The recruited ␤-catenin was thereafter transported to the nucleus, leading to cell growth These findings suggest that Siglec-9 expressed on immune cells may play a role as a potential counterreceptor for MUC1 and that this signaling may be another MUC1-mediated pathway and function in parallel with a growth factor-dependent pathway

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