Possible role of sialylation of retinal protein glycans in the regulation of electroretinogram response in mice

Abstract:

AIM: To evaluate if the nature, degree and extent of Siaα2-3-/Siaα2-6-sialylation of retinal protein glycans plays a possible role in the development and regulation of electroretinogram response (ERG) in mice. METHODS: Proteins extracted, from retinae of postnatal day 2 (PN2), PN7, and PN14 wild type (wt) and retinal degeneration 1 (rd1) mice were quantified, labeled and used for lectin-microarray profiling with immobilized lectins which recognize a wide range of N-/O-glycans. Net fluorescence intensities of lectin-ligand complexes were measured and images of fluorescent lectin-microarrays were acquired. From the binding curves between each lectin and protein extracts from PN14 wt and PN14 rd1 mice retinae, the protein concentration was selected to determine optimum signal intensity for lectin-ligand binding. Mean±SEM values of proteins and fluorescence-intensities of lectin-ligand-complexes between 45 lectins and 36 protein extracts from wt and rd1 mice retinae were compared for significance of differences. RESULTS: Comparison of the progressive relative changes in the sialylated glycans of retinal proteins from wt and rd1 mice showed that Siaα2-3Galβ1-4GlcNAc-glycans (but not Siaα2-6-glycans) were detectable and quantifiable from the retinal-proteins of PN7 and PN14 wt and rd1 mice. Siaα2-3-sialylation of retinal-protein Gal/α-linked-Gal-glycans was significantly increased with age in PN7 and PN14 wt and less so in PN14 rd1 mice. Siaα2-3-/Siaα2-6-sialylation of retinal-protein Gal/α-linked-Gal-glycans was absent in PN2 wt and rd1 mice. Comparison of published ERG responses of wt and rd1 mice retinae with degree of Siaα2-3-sialylation of retinal-protein-glycans showed that PN2 wt and rd1 mice lack both the ERG response and Siaα2-3-/Siaα2-6-sialylation of retinal-protein Gal/α-linked-Gal-glycans; rd1 mice with relatively lower Siaα2-3-sialylation of retinal-protein Gal/α-linked-Gal-glycans showed aberrant ERG response; and wt mice with significantly higher Siaα2-3-sialylation of retinal-protein Gal/α-linked-Gal-glycans showed normal ERG response. CONCLUSION: Degree of Siaα2-3-sialylation of glycans possibly regulates ERG function in mice.