P0071 and plakophilin signalling in the cytoplasm 
P0071 and plakophilins associate with the actin cytoskeleton and are involved in regulating actin organization. We have recently shown that p0071 associates and regulates RhoA at the cleavage furrow during cytokinesis (Wolf et al., 2006). Overexpression and knockdown of p0071 induced a cytokinesis defect that was mediated by up- or downregulation of RhoA activity at the contractile ring. There, p0071 interacted directly with RhoA itself and with the Rho-GEF Ect2. Full activation of RhoA required Ect2 as well as p0071 indicating that these two proteins act in conjunction to regulate RhoA during cytokinesis. 


p0071 localization at the centrosome and the midbody. Red: p0071; green: microtubules; blue: nucleus

Multinucleation after p0071 overexpression. Red: p0071; green: microtubules(left); actin (right); blue: nucleus 

Our hypothesis is that by controlling numerous stimulating guanine exchange factors (GEFs) and inhibiting GTPase activating proteins (GAPs) via the formation of multiprotein complexes at the "right time and place", p0071 may direct the spatio-temporal control of Rho-signalling. It is therefore possible that p120 family members coordinately regulate the activity of Rho-GTPases and the balance between cell adhesion and cell motility. The basic principle of action may be conserved but individual protein interactions with either upstream regulators or downstream effectors or both may vary between the family members. This may contribute to a precise temporal and spatial regulation of rho GTPase ensuring activation of specific effectors at the "right time and the right place".


Nuclear functions

Protein protein interactions in the nucleus are currently investigated to elucidate the signalling function of plakophilin 1 in the nucleus.






Localization of Plakophilin 1 in the nucleus 
and actin fibres