Milon, A. | bioRxiv Science

bioRxiv2019

The conical shape of DIM lipids promotes Mycobacterium tuberculosis infection of macrophages

Phthiocerol dimycocerosate (DIM) is a major virulence factor of the pathogen Mycobacterium tuberculosis (Mtb). While this lipid promotes the entry of Mtb into macrophages, which occurs via phagocytosis, its molecular mechanism of action is unknown. Here, we combined biophysical, cell biology, and modelling approaches to reveal the molecular mechanism of DIM action on macrophage membranes leading to the first step of Mtb infection. MALDI-TOF mass spectrometry showed that DIM molecules are transferred from the Mtb envelope to macrophage membranes during infection. Multi-scale molecular modeling and 31P-NMR experiments revealed that DIM adopts a conical shape in membranes and aggregate in the stalks formed between two opposing lipid bilayers. Infection of macrophages pre-treated with lipids of various shapes uncovered a general role for conical lipids in promoting phagocytosis. Taken together, these results reveal how the molecular shape of a mycobacterial lipid can modulate the biological function of macrophages.

biophysics↗

bioRxiv2018

Towards understanding biology of leydiogioma. G protein-coupled receptor and peroxisome proliferator-activated receptor crosstalk regulates lipid metabolism and steroidogenesis in Leydig cell tumors

Leydig cell tumors (LCT) are the most common type of testicular sex cord-stromal tumor. In this report, we implicate the G-coupled estrogen receptor (GPER) and peroxisome proliferator receptor (PPAR) in regulation of lipid homeostasis and the expression of steroidogenesis-controlling molecules in clinical specimens of LCTs and cell line (mouse tumor Leydig cells; MA-10). We also show the general structure and morphology of human LCTs with the use of scanning electron microscopy and light microscopy, respectively. In LCTs, protein immunoblotting and immunohistochemical analysis revealed increased expression of GPER and decreased expression of PPAR, {beta} and {gamma}. Concomitantly, changes in expression pattern of the lutropin receptor (LHR), protein kinase A (PKA), perilipin (PLIN), hormone sensitive lipase (HSL), steroidogenic acute regulatory protein (StAR), translocator protein (TSPO), HMG-CoA synthase (HMGCA), and HMG-CoA reductase (HMGCR) were observed.\n\nUsing MA-10 cells treated with GPER and PPAR antagonists (alone and in combination), we demonstrated there is a GPER-PPAR mediated control of cholesterol concentration. In addition, GPER-PPAR regulated estradiol secretion, while GPER-PPAR{gamma} affected cGMP concentration. It is assumed that GPER and PPAR can be altered in LCT, resulting in a perturbed lipid balance and steroidogenesis. In LCTs, the phosphatidylinositol-3-kinase (PI3K)-Akt-mTOR signaling pathway was disturbed. Thus, PI3K-Akt-mTOR, together with cGMP, can play a role in LCT proliferation, growth, and metastasis as well as lipid balance control.\n\nIn conclusion, we discuss the implications of GPER-PPAR interaction with lipid metabolism and steroidogenesis controlling-molecules in LCT biology that can be used in future studies as potential targets of diagnostic and therapeutic implementations.

physiology↗