Transfer of miRNA from single HDL particles to cells

Until recently communication between tissues was believed to occur solely via hormone-like substances. It becomes more and more clear that cellular communication is more complex than anticipated. Recently also genetic material was found to circulate in the blood stream, the so-called Micro-RNA (miRNA), which are short single stranded RNA molecules. These miRNAs regulate many biological processes and are known to play a role in the progression of atherosclerosis. In particular, extracellular miRNAs circulate stable in the bloodstream and were recognized as novel diagnostic markers. Recently two groups showed that high-density lipoprotein (HDL) transports and delivers functional miRNAs to the recipient cell. Still to date it has not been possible to observe the cellular release mechanism of miRNAs as they occur whether within a cell or at the cell membrane at a single molecule level. We hypothesize that miRNA delivery from HDL particles follows the lipid uptake path. We aim to unravel this transfer process beginning at the cell membrane to its final destination using high-end single molecule fluorescence and force microscopy which allows to image directly the uptake pathway of miRNA via HDL particles to the target cell.

 

 

 Czech-Austrian-Center for Supracellular Medical Research

Interdisciplinary research on the production of organ-like carrier structures.

 

 

 

 

 

 

 

 

 HDL holo-particle uptake maintains cellular cholesterol homeostasis

Cholesterol transport via high density lipoprotein (HDL) is an essential regulatory mechanism to remove excess cholesterol from peripheral tissue and to deliver it back to the liver for disposal. In contrast to the low density lipoprotein (LDL) receptor pathway, in which the entire LDL particle is degraded by the cell, HDL delivers only its core lipids to the cell, which is termed selective uptake.
In the present project we study holo-HDL particle uptake and resecretion as an alternative mechanism to maintain cholesterol homeostasis. This includes its physiological relevance as well as the receptors involved.

 

How to examine lipid trafficking at high resolution

We are characterizing the uptake of HDL and its lipid (free and esterified cholesterol) in detail by CLEM (combined light-electron microscopy). Therefore, diaminobenzidine photooxidation is utilized to convert fluorescent protein labels and cholesterol probes into electron dense precipitates. This method allows the localization of proteins and lipids at nanometer resolution by transmission electron microscopy and electron tomography.

 

 Lipoprotein modification alters cholesterol efflux capacity

Lipoproteins are modified in-vivo by in flammation, oxidative stress or altered renal function. We study the altered properties to exchange lipids between cells and lipoproteins and the molecular mechanism involved.