PMID: 27384988

 

    Legend: Sugar

Title : Ribosomal protein S3 ( rpS3 ) secreted from various cancer cells is N-linked glycosylated

Abstract :

1. Ribosomal protein S3 ( rpS3 ) is a 243 amino acid component of the 40S ribosomal small subunit
2. It has multiple roles in translation and extra-ribosomal functions like apoptosis and DNA repair
3. RpS3 is secreted only in cancer cell lines
4. Presently, mass spectrometry analysis revealed rpS3 to be glycosylated at the Asn165 residue
5. A point mutation at this residue decreased secretion of rpS3 in cancer cell lines
6. Secretion was also inhibited by the endoplasmic reticulum (ER)-Golgi transport inhibitor Brefeldin A and by Tunicamycin , an inhibitor of N-linked glycosylation
7. N-linked glycosylation of rpS3 was confirmed as necessary for rpS3 secretion into culture media via the ER-Golgi dependent pathway
8. RpS3 bound to Concanavalin A , a carbohydrate binding lectin protein , while treatment with peptide-N-glycosidase F shifted the secreted rpS3 to a lower molecular weight band
9. In addition, the N165G mutant of rpS3 displayed reduced secretion compared to the wild-type
10. An in vitro binding assay detected rpS3 homodimer formation via the N-terminal region ( rpS3 :1-85) and a middle region ( rpS3 :95-158)
11. The results indicate that the Asn 165 residue of rpS3 is a critical site for N-linked glycosylation and passage through the ER-Golgi secretion pathway