The Hippo pathway regulates organ size and tissue homeostasis in response to multiple stimuli, including cell density and mechanotransduction. Pharmacological inhibition of phosphatases can also stimulate Hippo signaling in cell culture. We recently defined the Hippo protein-protein interaction network with and without inhibition of serine and threonine phosphatases by okadaic acid. Interactions were captured using both standard affinity purification coupled to mass spectrometry and in vivo biotinylation, which we also coupled to mass spectrometry. We identified 749 protein interactions, including 599 previously unrecognized interactions, and demonstrated that several of them were phosphorylation-dependent. For example, we identified phospho-dependent interactions between a phosphatase module (PP6) and kinases in the pathway (MST1 and MST2) and the MOB1 co-activator of the LATS kinases. These interactions were enabled by a newly recognized phospho-binding domain on MOB1. Another set of signaling interactions were between the MST1 and MST2 kinases and the STRIPAK complex (Striatin interacting phosphatase and kinase); this interaction was mediated by a forkhead associated (FHA) domain in the STRIPAK subunit SLMAP (sarcolemmal membrane-associated protein). We will discuss the role of STRIPAK in both the Hippo pathway and in the vascular system homeostasis, as we first characterized its function in cerebral cavernous malformations.