Membrane microdomains or "lipid rafts", lateral complexes of distinct proteins and lipids, are implicated in a variety of functions like signal transduction, vesicle trafficking, sorting of certain proteins and lipids, and cell polarity. We investigate the functions of oligomeric membrane proteins that are typical lipid raft markers, the stomatins and flotillins, particularly in the context of cholesterol trafficking, membrane scaffolding and vesiculation. In a second project, we study red blood cell membrane microdomains in the context of cholesterol availability and associated morphological changes, as presented in the form of acanthocytes in the disease neuroacanthocytosis.
 
Stomatin-specific microdomains

Stomatin is an oligomeric, cholesterol-binding, lipid raft-associated, integral membrane protein that is localized to the cytoplasmic side of the plasma membrane and late endosomes of many cell types. We are studying the structure and function of stomatin focusing on oligomerization, cholesterol-binding, lipid raft-association, and interactions with other membrane proteins, such as the glucose transporter GLUT1. Moreover, we study the role of cholesterol in stomatin-GLUT1 complex formation. For our investigations we are using biochemical, molecular and cell biological methods, complemented by collaborative studies together with partners from the LIMES Institute, Univ. Bonn, the Institute of Biophysics, JKU Linz, and the IGMM, Univ. Montpellier.

European Multidisciplinary Initiative on Neuroacanthocytosis (EMINA)

An ERA-NET/E-RARE network coordinated by Prof. Adrian Danek (LMU, Munich) comprises six partner organizations in Germany, Austria, the Netherlands, France, and Turkey, to take a significant step forward in both basic research and applied clinical research into the neuroacanthocytosis (NA) syndromes. These syndromes are a group of rare neurological illnesses, which affect mostly young adults. NA is associated with neurodegeneration in the brain, similar to Huntington’s Disease, but can be differentiated by the presence of spiky erythrocytes (acanthocytes) in the blood. Several candidate genes for various NA forms have been identified: VPS13A (vacuolar protein sorting 13A) for chorea-acanthocytosis (ChAc), XK (Kell system) for McLeod Syndrome (MLS), JPH3 (junctophilin 3) for Huntington’s Disease-Like 2 (HDL2), and PANK2 (pantothenate kinase 2) for Pantothenate Kinase-Associated Neurodegeneration (PKAN). Our group participates in EMINA basic research by focusing on the identification of acanthocyte membrane domains that differ in composition from the normal, discocyte membrane. We hypothesize that the VPS13A defect will affect vesicle sorting and autophagy in late stage erythropoiesis and thus lead to changes during reticulocyte membrane reorganization. Similar sorting defects may affect autophagy in neurons leading to accumulation of protein aggregates and cell death.