Amnionless-mediated glycosylation is crucial for cell surface targeting of cubilin in renal and intestinal cells

Sci Rep. 2018 Feb 5;8(1):2351. doi: 10.1038/s41598-018-20731-4.

Tomohiro Udagawa ¹ ², Yutaka Harita ³, Kenichiro Miura ¹, Jun Mitsui ⁴, Koji L Ode ⁵, Shinichi Morishita ⁶, Seiya Urae ¹, Shoichiro Kanda ¹, Yuko Kajiho ¹, Haruko Tsurumi ¹, Hiroki R Ueda ⁵, Shoji Tsuji ⁴, Akihiko Saito ⁷, Akira Oka ¹

Affiliations

1 Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
2 Department of Pediatrics and Developmental Biology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
3 Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan. haritay-ped@h.u-tokyo.ac.jp.
4 Department of Neurology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
5 Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
6 Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba, 277-8561, Japan.
7 Department of Applied Molecular Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757, Asahimachidori, Chuo-ku, Niigata-shi, Niigata, 951-8510, Japan.

PMID: 29402915 DOI: 10.1038/s41598-018-20731-4

Abstract

Mutations in either cubilin (CUBN) or amnionless (AMN) genes cause Imerslund-Gräsbeck syndrome (IGS), a hereditary disease characterised by anaemia attributed to selective intestinal malabsorption of cobalamin and low-molecular weight proteinuria. Although cubilin protein does not have a transmembrane segment, it functions as a multi-ligand receptor by binding to the transmembrane protein, amnionless. We established a system to quantitatively analyse membrane targeting of the protein complex in cultured renal and intestinal cells and analysed the pathogenic mechanisms of mutations found in IGS patients. A novel CUBN mutation, several previously reported CUBN missense mutations and all previously reported AMN missense mutations resulted in endoplasmic reticulum (ER) retention and completely inhibited amnionless-dependent plasma membrane expression of cubilin. The ER retention of cubilin and amnionless was confirmed in renal proximal tubular cells of a patient with IGS. Notably, the interaction between cubilin and amnionless was not sufficient, but amnionless-mediated glycosylation of cubilin was necessary for their surface expression. Quantitative mass spectrometry and mutagenesis demonstrated that N-linked glycosylation of at least 4 residues of cubilin protein was required for its surface targeting. These results delineated the molecular mechanisms of membrane trafficking of cubilin in renal and intestinal cells.

Name
Email *

	Sorry, but the email address you supplied was invalid.