Adhesion of cells to the surrounding extracellular matrix and to other cells is essential for tissue integrity. In addition to this structural function, cell adhesion induces intracellular signaling mechanisms that regulate proliferation, apoptosis, cell polarity, differentiation and other processes. Cell attachment is mediated by specific receptors that can be grouped into various superfamilies based on structural similarities. Integrins are a family of heterodimeric transmembrane receptors consisting of an α and a β subunit. 18 different α and 8 different β subunits are known in mammals, which can combine to 24 different integrin receptors [1, 2]. The largest subgroup is formed by theβ1 subunit containing integrins which consist of 12 members with different ligand binding properties. All β1 integrins bind to extracellular matrix molecules: α1β1, α2β1, α10β1 and α11β1 are binding to collagen, α1β1, α2β1, α3β1, α6β1 and α7β1 to laminin, α4β1, α5β1, α8β1 and αvβ1 to fibronectin, α9β1 to tenascin C and αvβ1 to vitronectin. Some β1 integrin containing receptors also interact with cellular receptors: α4β1 and α9β1 bind to VCAM-1 and α4β1 to MadCAM-1. If ligands bind to integrin at the extracellular side, the cytoplasmic integrin tail connnects to the actin cytoskeleton and elicits various intracellular signaling pathways. Since integrin molecules lack an actin binding domain and any enzymatic activity, all these effects are mediated by integrin associated molecules. Currently more than 10 molecules are known that bind to the cytoplasmic tail of β1 integrin, and 5 which interact with the intracellular domain of β1 associated α sub-