Title : N-Glycosylation of
Human R-Spondin 1 Is Required for Efficient Secretion and Stability but
Not for Its Heparin Binding Ability
Abstract :
- R-spondin 1 ( Rspo1 ) plays an essential role in stem cell biology by potentiating Wnt signaling activity
- Despite the fact that Rspo1 holds therapeutic potential for a number of diseases, its biogenesis is not fully elucidated
- All Rspo proteins feature two amino-terminal furin-like repeats, which are responsible for Wnt signal potentiation, and a thrombospondin type 1 ( TSR1 ) domain that can provide affinity towards heparan sulfate proteoglycans
- Using chemical inhibitors, deglycosylase and site-directed mutagenesis, we found that human Rspo1 and Rspo3 are both N-glycosylated at N137 , a site near the C-terminus of the furin repeat 2 domain, and Rspo2 is N-glycosylated at N160 , a position near the N-terminus of TSR1 domain
- Elimination of N-glycosylation at these sites affects their accumulation in media but have no effect on the ability towards heparin
- Introduction of the N-glycosylation site to Rspo2 mutant at the position homologous to N137 in Rspo1 restored full glycosylation and rescued the accumulation defect of nonglycosylated Rspo2 mutant in media
- Similar effect can be observed in the N137 Rspo1 or Rspo3 mutant engineered with Rspo2 N-glycosylation site
- The results highlight the importance of N-glycosylation at these two positions in efficient folding and secretion of Rspo family
- Finally, we further showed that human Rspo1 is subjected to endoplasmic reticulum (ER) quality control in N-glycan-dependent manner
- While N-glycan of Rspo1 plays a role in its intracellular stability, it had little effect on secreted Rspo1
- Our findings provide evidence for the critical role of N-glycosylation in the biogenesis of Rspo1
Output (sent_index, trigger,
protein,
sugar,
site):
- 0. N-Glycosylation, , Human R-Spondin 1, -, -
- 10. Rspo1, , Rspo1, N-glycan, -
- 11. N-glycosylation, , Rspo1, -, -
- 4. N-glycosylated, , Rspo1, -, N137
- 4. N-glycosylated, , Rspo1, -, site
- 4. N-glycosylated, , Rspo2, -, N160
- 4. N-glycosylated, , Rspo2, -, position
- 4. N-glycosylated, , Rspo3, -, N137
- 4. N-glycosylated, , Rspo3, -, site
- 6. N-glycosylation, , -, -, site
- 7. N-glycosylation, , -, -, site
Output(Part-Of) (sent_index,
protein,
site):
- 3. TSR1, domain
- 3. thrombospondin type 1, domain
- 4. TSR1, domain
- 6. Rspo1, N137
- 7. Rspo2, site
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):
- 4. Rspo1, -, N137
- 4. Rspo2, -, N160
- 4. Rspo3, -, N137