Drosophila Rolling pebbles colocalises and putatively interacts with alpha-Actinin and the Sls isoform Zormin in the Z-discs of the sarcomere and with Dumbfounded/Kirre, alpha-Actinin and Zormin in the terminal Z-discs
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The rolling pebbles gene of Drosophila encodes two proteins, one of which, Rols7, is essential for myoblast fusion. In addition, Rols 7 is expressed during myofibrillogenesis and in the mature muscles. Here it overlaps with alpha-Actinin (α-Actn) and the N-terminus of D-Titin/Kettin/Zormin in the Z-line of the sarcomeres. In the attachment sites of the somatic muscles, Rols7 and the immunoglobulin superfamily protein Dumbfounded/Kin of irreC (Duf/Kirre) colocalise. As Duf/Kirre is detectable only transiently, it may be involved in establishing the first contact of the outgrowing muscle fiber to the epidermal attachment site. We propose that Rols7 and Duf/Kirre link the terminal Z-disc to the cell membrane by direct interaction. This is supported by the fact that in yeast two hybrid assays the tetratricopeptide repeat E (TPR E) of Rols7 shows interaction with the intracellular domain of Duf/Kirre. The colocalisation of Rols7 with α-Actn and with D-Titin/Kettin/Zormin in the Z-dics is reflected in␣interactions with different domains of Rols7 in this assay. In summary, these data show that besides the role in myoblast fusion, Rols7 is a scaffold protein during myofibrillogenesis and in the Z-line of the sarcomere as well as in the terminal Z-disc linking the muscle to the epidermal attachment sites.
KeywordsAttachment Site Ankyrin Repeat Muscle Attachment Body Wall Muscle Myoblast Fusion
We are grateful for providing clones and antibodies to Belinda Bullard and Deborah Andrew. We thank Christiana Stute and Belinda Bullard for critical reading of the manuscript. We thank Ruth Hyland for excellent technical assistance. This work was supported by the Deutsche Forschungsgemeinschaft (Re628/10-4 and Re628/14-1), the EU network of excellence MYORES, the Fonds der Chemischen Industrie to R.R.-P and the SFB 505 to K.F.F.
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