Browsing by Person "Strauch, Lisa"

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Funktionelle Charakterisierung der Phosphatase RDGC in Drosophila melanogaster Photorezeptorzellen
(2018) Strauch, Lisa; Huber, Armin
Phosphorylation of important components like rhodopsin and TRP plays a big role in the phototransduction cascade of Drosophila melanogaster. The analyzed phosphatase RDGC is needed for the dephosphorylation of both components. It is yet knwon thet RDGC is expressed in three isoforms which will be named RDGC-S, RDGC-M and RDGC-L. Nothing has been known about the origin of RDGC-M. The present work shows thet RDGC-M is generated by using an alternative translation start codon and an alternative splice site within the RNA of the short isoform. Analysis of the subcellular localization showed membrane assoziation of RDGC-M and -L whereas RDGC-S is found in the soluble fraction. Recominant expression in S2-cells identified acylation of RDGC-M and -L as the source of the membrane association. In addition, acylation of RDGC-L isolated from flies was directly proven by using a biochemical assay. To functionally characterize the three isoforms, mutant flies with different RDGC expression paterns were created and analyzed. As a result, it was shown that rhodopsin hyperphosphorylation that is found in the rdgc nullmutant as well as the associated retinal degeneration is prevented by the expression of any RDGC isoform. Regarding TRP channel phosphorylation none of the three isoforms is mandatory for the dephosphorylation of TRP at Ser936. However, the results revealed thet the total amount of RDGC that is available, in particular RDGC-M, affects the kinetics of the TRP-S936 dephosphorylation. An increased expression of RDGC-M in the absence of RDGC-S leads to a faster dephosphorylation of TRP-S936. Such a change in TRP-S936 dephosphorylation kinetics was not observed in flies overexpressing RDGC-S in an rdgc-nullmutangt backgroundand therefore cannot be attributed to the increased amount of the corresponding protein. Taken together this study shows thet the tgree RDGC isoforms differ in their subcellular localization due to differences in the N-termini. This may be the reason for kinetic differences in the dephosphorylation of TRP-S936 by RDGC-S or RDGC-M. Apart from these findings, all RDGC isoforms are able to dephosphorylate rhodopsin.