Abstract
BackgroundThe small G-protein Rap1 is an important regulator of cellular adhesion in Dictyostelium, however so far the downstream signalling pathways for cell adhesion are not completely characterized. In mammalian cells talin is crucial for adhesion and Rap1 was shown to be a key regulator of talin signalling.ResultsIn a proteomic screen we identified TalinB as a potential Rap1 effector in Dictyostelium. In subsequent pull-down experiments we demonstrate that the Ras association (RA) domain of TalinB interacts specifically with active Rap1. Studies with a mutated RA domain revealed that the RA domain is essential for TalinB-Rap1 interaction, and that this interaction contributes to cell-substrate adhesion during single-celled growth and is crucial for cell-cell adhesion during multicellular development.ConclusionsDictyostelium Rap1 directly binds to TalinB via the conserved RA domain. This interaction is critical for adhesion, which becomes essential for high adhesive force demanding processes, like morphogenesis during multicellular development of Dictyostelium. In mammalian cells the established Rap1-talin interaction is indirect and acts through the scaffold protein - RIAM. Interestingly, direct binding of mouse Rap1 to the RA domain of Talin1 has recently been demonstrated.Electronic supplementary materialThe online version of this article (doi:10.1186/s12860-015-0078-0) contains supplementary material, which is available to authorized users.
Highlights
The small G-protein Rap1 is an important regulator of cellular adhesion in Dictyostelium, so far the downstream signalling pathways for cell adhesion are not completely characterized
We showed that in vegetative cells Rap1-mediated adhesion depends on the presence of either TalinA or TalinB
Our studies further showed direct binding interaction between TalinB and Rap1, and the experiments with a TalinB mutant that is incapable of binding Rap1 revealed strongly diminished adhesion
Summary
The small G-protein Rap is an important regulator of cellular adhesion in Dictyostelium, so far the downstream signalling pathways for cell adhesion are not completely characterized. In mammalian cells talin is crucial for adhesion and Rap was shown to be a key regulator of talin signalling. The small G-protein Rap is critically involved in the regulation of cellular adhesion in many model organisms [3]. In the amoeba Dictyostelium discoideum Rap appears to have an essential role and is involved in regulating a multitude of cellular functions among which cell shape regulation, chemotaxis, substrate adhesion, multicellular development and cytokinesis [5,6,7,8,9,10]. Despite the important role of Dictyostelium Rap in regulating adhesion [11], the underlying signalling pathways are not fully understood. Only the Serine/Threonine Kinase Phg has been identified as a key component of the Rap1-mediated adhesion pathway [11]
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