Regulation of intracellular traffic by PI3P-binding proteins - a functional and ultrastructrural study

Many important cellular processes such as intracellular transport, signaling through growth hormone receptors, cell motility and apoptosis are regulated directly or indirectly by phosphatidylinositol (PI)-3-kinases. These kinases have different reaction products, one of these being PI-3-phosphates (PI3P), which mediate interactions with proteins containing so called FYVE domains or PX-domains. PI3P recruits these proteins onto specific cellular membranes thereby controlling their activity. Several of t hese FYVE proteins have been shown to be important regulators of the endocytic process and intracellular signalling, wheread others are involved in apoptosis and autophagy. We are studying several candidates involved in these processes. Hrs (hepatocyte g rowth factor receptor substrate) is a key regulator of the endocytic process, whereas Alfy (Autophagy linked FYVE-protein) is involved in the autophagic degradation of protein aggregates. Our goal is to define their function and to characterize possible interaction partners. We will also study the intracellular traffic of fibroblast growth factor (FGF-1) and are investigating from where this growth factor translocates into the cytosol and how it is transported into the nucleus. We will combine molecula r biology, biochemistry and microscopic methods in this study, with a special emphasis on the use of electron microscopical techniques for localization of proteins.