p.L571P in the linker domain of rat thyroglobulin causes intracellular retention
| Autor: | Peter Arvan, Karen G. Scheps, Héctor M. Targovnik, Cintia E. Citterio, Osvaldo Rey, Sofia Siffo, Christian M. Moya, Maricel F. Molina, Carina M. Rivolta, Mauricio Gomes Pio |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Male
0301 basic medicine DNA Complementary Glycoside Hydrolases Protein domain Mutant Intracellular Space 030209 endocrinology & metabolism medicine.disease_cause Thyroglobulin Biochemistry Protein Structure Secondary 03 medical and health sciences symbols.namesake 0302 clinical medicine Endocrinology Protein Domains Complementary DNA medicine Animals Humans Amino Acid Sequence Rats Wistar Molecular Biology Mutation Expression vector Base Sequence Chemistry Endoplasmic reticulum Point mutation Golgi apparatus Molecular biology HEK293 Cells 030104 developmental biology Mutagenesis symbols Mutant Proteins Protein Multimerization |
| Zdroj: | Molecular and Cellular Endocrinology. 505:110719 |
| ISSN: | 0303-7207 |
| Popis: | Thyroglobulin (TG), a large glycosylated protein secreted by thyrocytes into the thyroid follicular lumen, plays an essential role in thyroid hormone biosynthesis. Rattus norvegicus TG (rTG) is encoded by a large single copy gene, 186-kb long, located on chromosome 7 composed of 48 exons encoding a 8461-kb mRNA. Although the TG gene displays sequence variability, many missense mutations do not impose any adverse effect on the TG protein, whereas other nucleotide substitutions may affect its TG stability and/or TG intracellular trafficking. In order to gain a further understanding of the protein domains regulating its intracellular fate, we cloned a full-length cDNA from rTG into the pcDNA6/V5-His B expression vector. However, transient expression of the cDNA in HEK293T cells showed that the encoded protein was not a wild-type molecule, as it was unable to be secreted in the culture supernatant. Sequencing analyses revealed three random mutations, which accidentally emerged during the course of cloning: c.1712T>C [p.L571P] in the linker domain (amino acid positions 360 to 604), c.2027A>G [p.Q676R] in TG type 1-6 repeat and c.2720A>G [p.Q907R] in the TG type 1-7 repeat. Expression of cDNAs encoding a combination of two mutations [p.Q676R-p.Q907R], [p.L571P-p.Q907R] or [p.L571P-p.Q676R] indicated that any TG bearing the p.L571P substitution was trapped intracellularly. Indeed, we expressed the single point mutant p.L571P and confirmed that this point mutation was sufficient to cause intracellular retention of mutant TG in HEK293T cells. Endo H analysis showed that the p.L571P mutant is completely sensitive to the enzyme, whereas the will-type TG acquires full N-glycan modifications in Golgi apparatus. This data suggest that the p.L571P mutant contains the mannose-type N-glycan, that was added at the first stage of glycosylation. Complex-type N-glycan formation in the Golgi apparatus does not occur, consistent with defective endoplasmic reticulum exit of the mutant TG. Moreover, predictive analysis of the 3D linker domain showed that the p.L571P mutation would result in a significant protein conformational change. In conclusion, our studies identified a novel amino acid residue within the linker domain of TG associated with its conformational maturation and intracellular trafficking. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect