Abstract
Coronin proteins are evolutionary conserved WD repeat containing proteins that have been proposed to carry out different functions. In Dictyostelium, the short coronin isoform, coronin A, has been implicated in cytoskeletal reorganization, chemotaxis, phagocytosis and the initiation of multicellular development. Generally thought of as modulators of F-actin, coronin A and its mammalian homologs have also been shown to mediate cellular processes in an F-actin-independent manner. Therefore, it remains unclear whether or not coronin A carries out its functions through its capacity to interact with F-actin. Moreover, the interacting partners of coronin A are not known. Here, we analyzed the interactome of coronin A as well as its interaction with F-actin within cells and in vitro. Interactome analysis showed the association with a diverse set of interaction partners, including fimbrin, talin and myosin subunits, with only a transient interaction with the minor actin10 isoform, but not the major form of actin, actin8, which was consistent with the absence of a coronin A-actin interaction as analyzed by co-sedimentation from cells and lysates. In vitro, however, purified coronin A co-precipitated with rabbit muscle F-actin in a coiled-coil-dependent manner. Our results suggest that an in vitro interaction of coronin A and rabbit muscle actin may not reflect the cellular interaction state of coronin A with actin, and that coronin A interacts with diverse proteins in a time-dependent manner.
Highlights
The coronin protein family is comprised of a group of evolutionary conserved proteins that are characterized by the presence of a central Tryptophan-Aspartate (WD or WD-40) repeat-containing domain fused via a linker of variable length to a coiled-coil domain that is involved in homo-oligomerization [1,2]
Interactome analysis showed the association with a diverse set of interaction partners, including fimbrin, talin and myosin subunits, with only a transient interaction with the minor actin10 isoform, but not the major form of actin, actin8, which was consistent with the absence of a coronin A-actin interaction as analyzed by co-sedimentation from cells and lysates
Crn1 was found to co-precipitate with fails to directly bind (F-)actin [11], which is in accordance with the presence of a CA-like (Central region fused to an acidic region) domain in yeast Crn1 [12] that is known to be responsible for interactions with actin and Arp2/3 [13,14]
Summary
The coronin protein family is comprised of a group of evolutionary conserved proteins that are characterized by the presence of a central Tryptophan-Aspartate (WD or WD-40) repeat-containing domain fused via a linker of variable length to a coiled-coil domain that is involved in homo-oligomerization [1,2]. In contrast to the in vitro results showing robust interaction with rabbit muscle actin, of the 31 different actin genes expressed in Dictyostelium that encode for 15 different isoforms [48,49] we found only the minor actin-10 form to associate with coronin A in a coiled coil-dependent manner at 48 h, but not at 24 or 110 h. An indirect and labile interaction of coronin A with the cytoskeleton would be advantageous, making it quickly available for incorporation into other complexes
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