Einfluss des Glycosylierungsmusters auf die Basalaktivität von hTRPC3 und hTRPC6

In all processes of living as breathing and regulation of circuit members of the transient receptor potential (TRP-) channels take part. The whole TRP-superfamily can be divided into several families and subfamilies. The TRPC (canonical or classical)-family was described first and consists of seven members, which can be divided into four subfamilies. The TRPC3,6,7-subfamily of human beings called h (human) TRPC3,6,7 are receptor- or store-operated non-selective cation channels. They can be activated by diacylglycerol. Four of hTRPC3,6,7-proteins can build an homotetrameric or heterotetrameric cation channel. Because of these structural and functional similarities is was not clear, whether hTRPC3,6,7 have equal biophysical characteristics and can be changed vice versa. Additional it was not cleared, whether the extracellular glycosylation patterns determine biophysical characteristics. For theses examinations mutants of hTRPC3,6,7-proteins were created. By using patch clamp in whole-cell and single-channel configuration following statements could be made: 1. hTRPC3 has only one glycosylation pattern on the first extracellular loop (e1), on the contrary hTRPC6 has another one on the second extracellular loop (e2) 2. hTRPC3 builds functional cation channels with high basal activity and hereby significant difference to hTRPC6 exists 3. hTRPC6-N561Q (elimination of glycosylation on e2) and hTRPC6-N473Q-N561Q (elimination of glycosylation on e1 and e2) build functional cation channels with high basal activity as hTRPC3 does and as well significant differences to hTRPC6 exist 4. hTRPC3-E512N (applying glycosylation pattern on e2) builds functional cation channels with low basal activity and hereby differs to hTRPC3 significantly 5. glycosylation does not influence activation by applying histamine or carbachol So glycosylation determinate the basal activity of hTRPC3 and hTRPC6. HTRPC3 shows significantly higher basal activity as hTRPC6 has. Their biophysical characteristics differs. So our conclusion is, hTRPC3 and hTRPC6 would have different cellular function.