Actin-based motility underlies multiple cellular processes. Polymerisation of actin from the monomeric to the filamentous form is mediated by the Arp2/3 complex. This complex has to be activated to be functional. To date there are two families of proteins that directly bind and activate the Arp2/3 complex through a conserved DDW motif: Wiskott-Aldrich syndrome proteins and cortactin. Initially there was not functional relationship between them until we demonstrated that cortactin binds and activates N-WASP via its SH3 domain. Thus cortactin can activate actin synthesis directly through its N-terminal DDW motif, or indirectly by binding to N-WASP via its c-terminal SH3 domain. Furthermore we demonstrated that cortactin activation of N-WASP is positive/negatively regulated by erk/src phosphorylation of cortactin respectively, probably by regulating the accessibility of its SH3 domain.
Based on these in vitro experiments, we proposed a switch on/off mechanism, which could be an important control mechanism of acti n remodelling. Thus cortactin has emerged as a multidomain protein that acts as a scaffold that redistributes signals to promote Arp2/3 complex mediated actin synthesis in a variety of cellular processes. The major objective of the project is the validation of the model in vivo.
The questions we will try to address are:
1) Cortactin is considered an oncogene. How is the activation state of cortactin contributing to its oncogenic potential?
2) Cortactin redistributes from the cytoplasm to the cortical cytoskeleton. How is the switch affecting its localization? Are there differences in the final actin structure formed? Is it regulating cortactin binding pattern?
3) Cortactin is implicated in pedestal formation by EPEC. Is the switch implicated in pedestal formation or in the underlying diarrhoea? The relevance of translating this model to in vivo settings has already being discussed enthusiastically by the scientist community.
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