Asparagine （Asn/N）-Iinked glycans are important for protein folding, trafficking, and endoplasmic reticulum-associated degradation in eukaryotes. The maturation of glycoproteins involves the trimming of mannosyl res...Asparagine （Asn/N）-Iinked glycans are important for protein folding, trafficking, and endoplasmic reticulum-associated degradation in eukaryotes. The maturation of glycoproteins involves the trimming of mannosyl residues by mannosidases and addition of other sugar molecules to three-branched N-glycans in the Golgi. However, the biological importance of Golgi-mediated mannose trimming is not fully understood. Here, we show that abolishment of two functionally redundant mannosidases, MNS1 and MNS2, responsible for α-1,2-mannose trimming on the A and C branches of plant N-glycans lead to severe root growth inhibition under salt stress conditions in Arabidopsis. In contrast, mutants with defects in the biosynthesis of the oligosaccharide precursor displayed enhanced salt tolerance in the absence of mannose trimming. However, mutation in EBS3, which is required for the formation of the branched N-glycan precursor, suppressed the salt-sensitive phenotype of mnsl mns2 double mutant. Interestingly, we observed that cellulose biosynthesis was compromised in mnsl mns2 roots under high salinity. Consistently, abundance of a membrane anchored endo-13-1,4-endoglucanase （RSW2/KOR） that plays a key role in cellulose biosynthesis and its mutant variant rsw2-1 were modulated by α-1,2-mannose trimming under salt stress. Overexpression of RSW2 could partially rescue the salt-sensitive phenotype of mnsl mns2. Taken together, these results suggest that MNS1/2-mediated mannose trimming of N-glycans is crucial in modulating glycoprotein abundance to withstand salt stress in plants.展开更多
Pulmonary surfactant is a lipid-protein complex secreted by alveolar typeⅡepithelial cells and is essential for the maintenance of the delicate structure of mammalian alveoli to promote efficient gas exchange across ...Pulmonary surfactant is a lipid-protein complex secreted by alveolar typeⅡepithelial cells and is essential for the maintenance of the delicate structure of mammalian alveoli to promote efficient gas exchange across the air-liquid barrier.The Golgi apparatus plays an important role in pulmonary surfactant modification and secretory trafficking.However,the physiological function of the Golgi apparatus in the transport of pulmonary surfactants is unclear.In the present study,deletion of GM130,which encodes for a matrix protein of the cis-Golgi cisternae,was shown to induce the disruption of the Golgi structure leading to impaired secretion of lung surfactant proteins and lipids.Specifically,the results of in vitro and in vivo analysis indicated that the loss of GM130 resulted in trapping of Sftpa in the endoplasmic reticulum,Sftpb and Sftpc accumulation in the Golgi apparatus,and an increase in the compensatory secretion of Sftpd.Moreover,global and epithelial-specific GM130 knockout in mice resulted in an enlargement of alveolar airspace and an increase in alveolar epithelial autophagy;however,surfactant repletion partially rescued the enlarged airspace defects in GM130-deficient mice.Therefore,our results demonstrate that GM130 and the mammalian Golgi apparatus play a critical role in the control of surfactant protein secretion in pulmonary epithelial cells.展开更多
基金This work was partly supported by grants from the National Natural Science Foundation--Outstanding Youth Foundation of China （grant no. 31322008） and the National Basic Research Program of China （grant no. 2014CB542300） to Z.H.
文摘Asparagine （Asn/N）-Iinked glycans are important for protein folding, trafficking, and endoplasmic reticulum-associated degradation in eukaryotes. The maturation of glycoproteins involves the trimming of mannosyl residues by mannosidases and addition of other sugar molecules to three-branched N-glycans in the Golgi. However, the biological importance of Golgi-mediated mannose trimming is not fully understood. Here, we show that abolishment of two functionally redundant mannosidases, MNS1 and MNS2, responsible for α-1,2-mannose trimming on the A and C branches of plant N-glycans lead to severe root growth inhibition under salt stress conditions in Arabidopsis. In contrast, mutants with defects in the biosynthesis of the oligosaccharide precursor displayed enhanced salt tolerance in the absence of mannose trimming. However, mutation in EBS3, which is required for the formation of the branched N-glycan precursor, suppressed the salt-sensitive phenotype of mnsl mns2 double mutant. Interestingly, we observed that cellulose biosynthesis was compromised in mnsl mns2 roots under high salinity. Consistently, abundance of a membrane anchored endo-13-1,4-endoglucanase （RSW2/KOR） that plays a key role in cellulose biosynthesis and its mutant variant rsw2-1 were modulated by α-1,2-mannose trimming under salt stress. Overexpression of RSW2 could partially rescue the salt-sensitive phenotype of mnsl mns2. Taken together, these results suggest that MNS1/2-mediated mannose trimming of N-glycans is crucial in modulating glycoprotein abundance to withstand salt stress in plants.
基金supported by the National Natural Sciences Foundation of China(31730051 and 31601164)the National Key Research and Development Program of China(2018YFA0800900)+1 种基金Natural Science Foundation of Shandong Province,China(ZR2019PH076)the Open Project of Forensic Medicine Key Laboratory of Shanxi Province,China(SFM2019001)。
文摘Pulmonary surfactant is a lipid-protein complex secreted by alveolar typeⅡepithelial cells and is essential for the maintenance of the delicate structure of mammalian alveoli to promote efficient gas exchange across the air-liquid barrier.The Golgi apparatus plays an important role in pulmonary surfactant modification and secretory trafficking.However,the physiological function of the Golgi apparatus in the transport of pulmonary surfactants is unclear.In the present study,deletion of GM130,which encodes for a matrix protein of the cis-Golgi cisternae,was shown to induce the disruption of the Golgi structure leading to impaired secretion of lung surfactant proteins and lipids.Specifically,the results of in vitro and in vivo analysis indicated that the loss of GM130 resulted in trapping of Sftpa in the endoplasmic reticulum,Sftpb and Sftpc accumulation in the Golgi apparatus,and an increase in the compensatory secretion of Sftpd.Moreover,global and epithelial-specific GM130 knockout in mice resulted in an enlargement of alveolar airspace and an increase in alveolar epithelial autophagy;however,surfactant repletion partially rescued the enlarged airspace defects in GM130-deficient mice.Therefore,our results demonstrate that GM130 and the mammalian Golgi apparatus play a critical role in the control of surfactant protein secretion in pulmonary epithelial cells.
