The role of actin isoforms and posttranslational modifications for cytoskeletal dynamics in the amoeba Dictyostelium discoideum

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Conventional actin is a highly conserved protein in all eukaryotes and well understood as the backbone of the microfilamentous system. However, very little is known about actin isoforms which do not belong to the tissue specific conventional ,, actin species. Do they copolymerize, form highly specific filaments, cap or crosslink or sever conventional actin filaments, are they subunits of larger protein complexes, are actin isoforms posttranslationally modified and thus regulated in structure and function? This proposal aims (a) at understanding of an entire actin system, and (b) at arginylation as an important posttranslational modification for cytoskeletal activities. The amoeba Dictyostelium discoideum is an ideal model system for these studies because the whole set of actin isoforms is known, and the system is amenable for sophisticated techniques of cell biology, molecular genetics, protein expression, and protein biochemistry. Identification of the individual actin isoforms, their expression patterns, arginylation and subcellular distribution will be important experimental approaches. In parallel, molecular genetics, expression of distinct constructs and biochemistry on the expressed actins and hybrids will then tell us how actin isoforms and their modifications help to orchestrate a complex cytoskeletal system.