We are expanding the range of assay techniques that will allow us to understand the sulfation code in chondroitin sulfate glycosaminoglycan (CS-GAG) chains. These assay techniques take advantage of specific chromatography techniques (ion exchange, hydrophilicity) to separate the different disaccharides and monosaccharides that comprise the GAG chains. This is the only technique capable of doing this. We have also initiated mass spectrometric analysis of these separated GAG chains to begin to determine the sequence of sulfations on the different parts of the GAG chain. Our results indicate that the sulfation pattern of the non-reducing end of the GAG chain is a major determinant of CS signaling. A patent was awarded based on our research and a publication describing these results is in preparation. We have conducted studies showing that the the LAR family of receptor protein tyrosine phosphatases are are binding partners for CS GAG chains. The binding of the different family members are not all the same. We have identified different regions in the extracellular domains of these molecules that bind GAG chains with different sulfation patterns. In addition our data point to an additional receptor that binds bioactive CSPGs. A publication describing these results is in preparation. We identified the protein plasticity related gene-3 (PRG-3) as one whose phosphorylation changes in response to chondroitin sulfate proteoglycans. PRG-3 is a member of a family of PRGs and our data indicate that these proteins interact to cause physiological changes in cells. A publication describing these results is in preparations. We demonstrated that astrocyte reactivity in response to TGF-βis dependent on the activity of a calcium-activated potassium channel KCa3.1. Pharmacological antagonism or knockout of this channel eliminates glial reactivity in response to TGF-β. Moreover, this is dependent upon the SMAD family of transcription factors.
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