The Pfeffer Lab is studying how human cells put receptors in the right place. We seek to elucidate the molecular mechanisms by which receptors are transported between specific membrane compartments in cells and how LDL derived cholesterol is exported from lysosomes. We are pioneers in the study of Rab GTPases that are master regulators of receptor trafficking. Rab GTPase phosphorylation by the LRRK2 kinase was recently linked to familial Parkinson’s Disease. We have discovered a Hedgehog signaling pathway that is likely to be blocked in specific neurons in the brain upon Rab phosphorylation, and we are testing a model that may explain in molecular detail, how this event leads to Parkinson’s Disease.