Nephrin is a member of the Super-IgG-Molecule family and is most prominently expressed in kidney podocytes. It is a major if not the most important structural component of the slit diaphragm, a modified adherens junction in between these cells. Nephrin is composed of an extracellular domain with eight distal IgG like domains and one proximal fibronectin type III domain, a transmembrane domain and a short intracellular domain. Nephrin molecules show both homophilic and heterophilic interactions. Among heterophilic interaction partners slit diaphragm proteins such as NEPH1, NEPH2 and NEPH3 were shown to stabilize the slit diaphragm structure. Intracellularly Podocin, CD2 associated protein (CD2AP) and adherins junction associated proteins like IQGAP, MAGI, CASK and spectrins were all shown to interact with nephrin. Hence nephrin seems to play a major role in organizing the molecular structure of the slit diaphragm itself and via its binding partners links it to the actin cytoskeleton. Nephrin does not only fulfill static properties within the slit diaphragm but by tyrosine phosphorylation of its cytoplasmic tail by the Src kinase Fyn it initiates the PI3K AKT signaling cascade which seems to promote antiapoptotic signals.