Identification Of Glycosylation In Silkworm Proteome And Its Potential Functions

Glycosylation refers to the covalent attachment of sugar residues to a protein or lipid,and the biological importance of this modification has been widely recognized.One of the major roles of glycans and glycoconjugates on the cell surface is acting as the receptor for outside pathogens such as viruses.During the initial stage of viral replication,virus interacts with cell membrane receptors,which are in many cases glycoproteins.Identifying such glycoproteins are essential in understanding the mechanisms of viral infection as well as developing antiviral strategies.Silkworm is an important economic insect as well as a model organism for molecular biology,yet current knowledge on its glycoproteome has been far from complete due to both analytical challenges as well as lack of perceived importance.Investigation on invertebrate glycosylation,especially on model organisms,not only expands the structural and functional knowledgebase,but also can facilitate deeper understanding on the biological functions of glycosylation in higher organisms.Therefore,in this study,the differences of glycosylation sites and glycoprotein sugar chains between different silkworm strains,and after virus infection,were characterized,which can provide an insight into role of glycosylation in viral recognition and infection processes.The main contents and results of this study are:1.To explore the effect of viral infection on the glycosylation level of silkworm proteins,silkworm strain P50 was infected with Bm CPV.In the total glycoproteome of the virus-infected silkworm,4 N-glycoproteins were first found to be Bm CPV-encoded.389 N-glycoproteins were identified in the P50 control and Bm CPV-infected groups,the glycosylation sites and glycans were different in the P50 and the Bm CPV-infected strains.A total of 13 O-glycoproteins were mapped in the P50 and its Bm CPV-infected strains.2.Prediction of the subcellular localization of the P50 glycoproteins.Quantitative comparison of glycoprotein analysis the P50 and Bm CPV-infected,there were 41 differentially regulated glycoproteins were categorized in metabolic processes,cell adhesion as well as in response to stimulus,indicating a change of molecular interactions by the virus infection.3.To explore the intrinsic difference in protein glycosylation of silkworm strains,the Bm NPV susceptible and resistant strains 306 and NB was used to characterize and compare their glycosylation levels.A total of 409 glycoproteins were identified in the silkworm.A total of 336 and 337 N-glycoproteins are mapped to the 306 and NB strains,respectively,with 264 glycoproteins shared by both strains.4.Comparison of glycoprotein glycosylation differences between NB and 306 in silkworm.Of the 72 N-glycoproteins unique to 306,27 of them have been evidenced at the protein,transcript,or gene level,or at least from homology.Four of the 27 unique N-glycoproteins to the 306 strain are predicted to be transmembrane glycoproteins,which are of particular interest as they can be potential cell surface targets during viral infections.For the Bm NPV resistant strains,a total of 73 N-glycoproteins are mapped,and 23 of them showed evidence for presence.However,none of 23 are transmembrane proteins,indicating the possibility of lacking cell surface glycoconjugates in the resistant strain.