The unfolded protein response in a dolichyl phosphate mannose-deficient Chinese hamster ovary cell line points out the key role of a demannosylation step in the quality-control mechanism of N-glycoproteins

2002 ◽  
Vol 362 (2) ◽  
pp. 491-498 ◽  
Author(s):  
François FOULQUIER ◽  
Anne HARDUIN-LEPERS ◽  
Sandrine DUVET ◽  
Ingrid MARCHAL ◽  
Anne Marie MIR ◽  
...  
Keyword(s):  
Quality Control ◽  
Control System ◽  
Unfolded Protein Response ◽  
Cell Line ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster ◽  
Quality Control System ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

The CHO (Chinese hamster ovary) glycosylation mutant cell line, B3F7, transfers the truncated glycan Glc3Man5GlcNAc2 on to nascent proteins. After deglucosylation, the resulting Man5GlcNAc2 glycan is subjected to two reciprocal enzymic processes: the action of an endoplasmic-reticulum (ER) kifunensine-sensitive α1,2-mannosidase activity to yield a Man4GlcNAc2 glycan, and the reglucosylation involved in the quality-control system which ensures that only correctly folded glycoproteins leave the ER. We show that the recombinant secreted alkaline phosphatase (SeAP) produced in stably transfected B3F7 cells, is co-immunoprecipitated with the GRP78 (glucose-regulated protein 78), a protein marker of the unfolded protein response (UPR). The level of GRP78 transcription has been evaluated by reverse transcription-PCR (RT-PCR) and we demonstrate that B3F7 cells present a constitutively higher level of UPR in the absence of inductors, compared with Pro−5 cells. Interestingly, a decrease was observed in the UPR and an increase in SeAP secretion in the kifunensine-treated B3F7 cells. Altogether, these data highlight the relationships between the glycan structure, the quality control system and the UPR. Moreover, they support the idea that a specific demannosylation step is a key event of the glycoprotein quality control in B3F7 cells.

scholarly journals Two Distinctly Localized P-Type ATPases Collaborate to Maintain Organelle Homeostasis Required for Glycoprotein Processing and Quality Control

2002 ◽  
Vol 13 (11) ◽  
pp. 3955-3966 ◽  
Author(s):  
Shilpa Vashist ◽  
Christian G. Frank ◽  
Claude A. Jakob ◽  
Davis T.W. Ng
Keyword(s):  
Quality Control ◽  
Unfolded Protein Response ◽  
Secretory Pathway ◽  
Ion Homeostasis ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Coa Reductase ◽  
Protein Response ◽  
P Type ◽  
Er Homeostasis

Membrane transporter proteins are essential for the maintenance of cellular ion homeostasis. In the secretory pathway, the P-type ATPase family of transporters is found in every compartment and the plasma membrane. Here, we report the identification of COD1/SPF1(control of HMG-CoA reductase degradation/SPF1) through genetic strategies intended to uncover genes involved in protein maturation and endoplasmic reticulum (ER)-associated degradation (ERAD), a quality control pathway that rids misfolded proteins. Cod1p is a putative ER P-type ATPase whose expression is regulated by the unfolded protein response, a stress-inducible pathway used to monitor and maintain ER homeostasis. COD1 mutants activate the unfolded protein response and are defective in a variety of functions apart from ERAD, which further support a homeostatic role.COD1 mutants display phenotypes similar to strains lacking Pmr1p, a Ca2+/Mn2+pump that resides in the medial-Golgi. Because of its localization, the previously reported role of PMR1 in ERAD was somewhat enigmatic. A clue to their respective roles came from observations that the two genes are not generally required for ERAD. We show that the specificity is rooted in a requirement for both genes in protein-linked oligosaccharide trimming, a requisite ER modification in the degradation of some misfolded glycoproteins. Furthermore, Cod1p, like Pmr1p, is also needed for the outer chain modification of carbohydrates in the Golgi apparatus despite its ER localization. In strains deleted of both genes, these activities are nearly abolished. The presence of either protein alone, however, can support partial function for both compartments. Taken together, our results reveal an interdependent relationship between two P-type ATPases to maintain homeostasis of the organelles where they reside.

scholarly journals Activation of Mammalian Unfolded Protein Response Is Compatible with the Quality Control System Operating in the Endoplasmic Reticulum

2004 ◽  
Vol 15 (6) ◽  
pp. 2537-2548 ◽  
Author(s):  
Satomi Nadanaka ◽  
Hiderou Yoshida ◽  
Fumi Kano ◽  
Masayuki Murata ◽  
Kazutoshi Mori
Keyword(s):  
Quality Control ◽  
Endoplasmic Reticulum ◽  
Control System ◽  
Golgi Apparatus ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Secretory Pathway ◽  
Unfolded Proteins ◽  
Unfolded Protein ◽  
Protein Response

Newly synthesized secretory and transmembrane proteins are folded and assembled in the endoplasmic reticulum (ER) where an efficient quality control system operates so that only correctly folded molecules are allowed to move along the secretory pathway. The productive folding process in the ER has been thought to be supported by the unfolded protein response (UPR), which is activated by the accumulation of unfolded proteins in the ER. However, a dilemma has emerged; activation of ATF6, a key regulator of mammalian UPR, requires intracellular transport from the ER to the Golgi apparatus. This suggests that unfolded proteins might be leaked from the ER together with ATF6 in response to ER stress, exhibiting proteotoxicity in the secretory pathway. We show here that ATF6 and correctly folded proteins are transported to the Golgi apparatus via the same route and by the same mechanism under conditions of ER stress, whereas unfolded proteins are retained in the ER. Thus, activation of the UPR is compatible with the quality control in the ER and the ER possesses a remarkable ability to select proteins to be transported in mammalian cells in marked contrast to yeast cells, which actively utilize intracellular traffic to deal with unfolded proteins accumulated in the ER.

scholarly journals Modulating protein quality control

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Lars Plate ◽  
Ryan J Paxman ◽  
R Luke Wiseman ◽  
Jeffery W Kelly
Keyword(s):  
Quality Control ◽  
Small Molecules ◽  
Unfolded Protein Response ◽  
Protein Misfolding ◽  
Protein Quality ◽  
Protein Quality Control ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Misfolding Diseases ◽  
Protein Response

Small molecules that modulate the unfolded protein response have the potential to treat a variety of human protein misfolding diseases.

The flavonoid tangeretin activates the unfolded protein response and synergizes with imatinib in the erythroleukemia cell line K562

2010 ◽  
Vol 54 (6) ◽  
pp. 823-832 ◽  
Author(s):  
Sofie Lust ◽  
Barbara Vanhoecke ◽  
Mireille Van Gele ◽  
Jan Philippé ◽  
Marc Bracke ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Cell Line ◽  
Unfolded Protein ◽  
Erythroleukemia Cell ◽  
The Unfolded Protein Response ◽  
Protein Response
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