Author
Kenichi Kamata (Nihon Univ), Yuki Fujii, Yukiko Ogawa (Nagasaki Int Univ), Marco Gerdol (Univ of Trieste), Hiyori Hatazawa, Izuru Sasaki, Kenshin Sasaki, Hinata Kiyohara, Suzuna Yoshimoto, Namiho Matsuzaki, Keita Yamamoto, Mayuka Ohkawa, Satoshi Odo, Masao Yamada, Yasuhiro Ozeki (Yokohama City Univ)
Keywords
Gel permeation chromatography, Lectins, HPLC, Sponges, Chondrilla australiensis
Abstract
Glycans, complex sugar chains decorating cell surfaces, play essential roles in recognition, adhesion, and signaling. Lectins, glycan-binding proteins, are widely conserved across species, but galectins in vertebrates typically lack classical secretion signals. In this study, we identified a novel lectin, hRTL, from the sponge Chondrilla australiensis. Initial hemagglutination assays revealed lactose-inhibitable binding activity. Using affinity chromatography, MALDI-TOF MS, and gel filtration HPLC, hRTL was purified and determined to be a tetrameric lectin with an approximate molecular weight of 60 kDa. Transcriptome analysis confirmed six related genes encoding hRTL, all containing N-terminal signal peptides̶an unusual feature for galectins, suggesting secretion into the extracellular milieu. Functional glycan array assays showed that hRTL specifically binds cancer-associated glycans, including TF antigen and Type-3 H antigen, as well as iPS cell-specific Type-1 LacNAc. In cell-based assays, hRTL selectively suppressed proliferation of human colon cancer cells (DLD-1) in a dose-dependent manner, while exerting weaker effects on other cancer lines. These results highlight hRTL as a structurally unique, secreted galectin with potent anti-tumor activity. Our findings suggest that ancestral galectins may have evolved as secreted defense molecules, and hRTL represents a promising candidate for novel glycan-targeted therapeutics.