We found that BMP2 was able to in crease the speed of C2C12 wound closure relative to a non stimulated control within 14 hours. Add itionally, knock down of p55�� impaired BMP2 induced wound closure compared to control transfected they cells. Intriguingly, we found that knock down of p55�� sig nificantly reduced the ability of cells to efficiently enter the wound in a BMP2 dependent fashion. We also investigated the relative Inhibitors,Modulators,Libraries migration of p55�� knock down cells compared to scrambled transfected cells by seeding a salt and pepper mix within the same wound. p55�� knock down cells displayed considerably Inhibitors,Modulators,Libraries impaired polarity and thus re duced ability to efficiently enter the wound, instead dis playing short trajectories compared to control cells.

Next, we performed a trans well assay to analyse whether the effect of BMP2 induced migration becomes more prominent when cells are ex posed to a ligand gradient. We found that BMP2 induced transmigration Inhibitors,Modulators,Libraries of C2C12 cells, whereas knock down of p55�� or LL5B significantly impaired this response. Collectively, our results demonstrate that the BMPRII p55�� interaction is necessary for BMP2 induced class Ia PI3K activation via the BMPRII p55�� interaction and PIP3 production via p110 activity at the leading edge cytocortex. Moreover, we showed that the BMP2 induced activation of PI3K is critically involved in actin reorganisation and lamellipodia formation Inhibitors,Modulators,Libraries due to the production of PIP3 and LL5B recruitment. With LL5B, we found an important PIP3 effector and actin regulator through its well described role in tethering filamins to the cytocortex.

p55��, p110 and LL5B, therefore, critically influence BMP2 induced chemotaxis with p55�� Inhibitors,Modulators,Libraries being a novel and specific BMPRII interacting protein required for chemotactic mesenchymal progenitor cell responses to BMP2. Discussion Since the initial discovery that BMPs act as chemotactic guidance cues, the molecular blog of sinaling pathways mechanism of how BMPs initiate cell migration and chemotaxis has remained poorly understood. However, an important role for BMP induced cell migration has been demonstrated in several excellent developmental, repair and disease stud ies. Here, we aimed to close a gap in the mechanis tic molecular understanding of how BMPs in general activate PI3K signalling in progenitor cells at the molecu lar level and how this influences actin reorganisation at the cytocortex and, hence, lamellipodia formation. We uncovered major and crucial aspects of the molecular mechanism by which BMP2 initiates and extends PI3K signalling at the plasma membrane, visualised and local ised BMP2 induced PIP3 for the first time in intact cells, and confirmed the requirement of p55�� and LL5B for BMP2 induced migration and chemotaxis of mesenchy mal progenitor cells.