Search results for "membrane"

Direct observation of alpha-lactalbumin, adsorption and incorporation into lipid membrane and formation of lipid/protein hybrid structures

2019

The interaction between proteins and membranes is of great interest in biomedical and biotechnological research for its implication in many functional and dysfunctional processes. We present an experimental study on the interaction between model membranes and alpha-lactalbumin (alpha-La). alpha-La is widely studied for both its biological function and its anti-tumoral properties. We use advanced fluorescence microscopy and spectroscopy techniques to characterize alpha-La-membrane mechanisms of interaction and alpha-La-induced modifications of membranes when insertion of partially disordered regions of protein chains in the lipid bilayer is favored. Moreover, using fluorescence lifetime imag…

Prooxidative chain transfer activity by thiol groups in biological systems

2020

Cysteine is arguably the best-studied biological amino acid, whose thiol group frequently participates in catalysis or ligand binding by proteins. Still, cysteine's unusual biological distribution has remained mysterious, being strikingly underrepresented in transmembrane domains and on accessible protein surfaces, particularly in aerobic life forms (“cysteine anomaly”). Noting that lipophilic thiols have been used for decades as radical chain transfer agents in polymer chemistry, we speculated that the rapid formation of thiyl radicals in hydrophobic phases might provide a rationale for the cysteine anomaly. Hence, we have investigated the effects of dodecylthiol and related compounds in i…

The expanding functional roles and signaling mechanisms of adhesion G protein-coupled receptors.

2019

The adhesion class of G protein-coupled receptors (GPCRs) is the second largest family of GPCRs (33 members in humans). Adhesion GPCRs (aGPCRs) are defined by a large extracellular N-terminal region that is linked to a C-terminal seven transmembrane (7TM) domain via a GPCR-autoproteolysis inducing (GAIN) domain containing a GPCR proteolytic site (GPS). Most aGPCRs undergo autoproteolysis at the GPS motif, but the cleaved fragments stay closely associated, with the N-terminal fragment (NTF) bound to the 7TM of the C-terminal fragment (CTF). The NTFs of most aGPCRs contain domains known to be involved in cell-cell adhesion, while the CTFs are involved in classical G protein signaling, as well…

2019

The effects of ionotropic γ-aminobutyric acid receptor (GABA-A, GABAA) activation depends critically on the Cl−-gradient across neuronal membranes. Previous studies demonstrated that the intracellular Cl−-concentration ([Cl−]i) is not stable but shows a considerable amount of activity-dependent plasticity. To characterize how membrane properties and different molecules that are directly or indirectly involved in GABAergic synaptic transmission affect GABA-induced [Cl−]i changes, we performed compartmental modeling in the NEURON environment. These simulations demonstrate that GABA-induced [Cl−]i changes decrease at higher membrane resistance, revealing a sigmoidal dependency between both par…

FRET biosensor allows spatio-temporal observation of shear stress-induced polar RhoGDIα activation

2018

Rho GDP-dissociation inhibitor α (RhoGDIα) is a known negative regulator of the Rho family that shuts off GDP/GTP cycling and cytoplasm/membrane translocation to regulate cell migration. However, to our knowledge, no reports are available that focus on how the RhoGDIα-Rho GTPases complex is activated by laminar flow through exploring the activation of RhoGDIα itself. Here, we constructed a new biosensor using fluorescence resonance energy transfer (FRET) technology to measure the spatio-temporal activation of RhoGDIα in its binding with Rho GTPases in living HeLa cells. Using this biosensor, we find that the dissociation of the RhoGDIα-Rho GTPases complex is increased by shear stress, and i…

Photoactivatable Adhesive Ligands for Light-Guided Neuronal Growth

2018

Neuro-regeneration after trauma requires growth and reconnection of neurons to reestablish information flow in particular directions across the damaged tissue. To support this process, biomaterials for nerve tissue regeneration need to provide spatial information to adhesion receptors on the cell membrane and to provide directionality to growing neurites. Here, photoactivatable adhesive peptides based on the CASIKVAVSADR laminin peptidomimetic are presented and applied to spatiotemporal control of neuronal growth to biomaterials in vitro. The introduction of a photoremovable group [6-nitroveratryl (NVOC), 3-(4,5-dimethoxy-2-nitrophenyl)butan-2-yl (DMNPB), or 2,2′-((3′-(1-hydroxypropan-2-yl)…

Unicellular ancestry and mechanisms of diversification of Goodpasture antigen-binding protein.

2018

The emergence of the basement membrane (BM), a specialized form of extracellular matrix, was essential in the unicellular transition to multicellularity. However, the mechanism is unknown. Goodpasture antigen–binding protein (GPBP), a BM protein, was uniquely poised to play diverse roles in this transition owing to its multiple isoforms (GPBP-1, -2, and -3) with varied intracellular and extracellular functions (ceramide trafficker and protein kinase). We sought to determine the evolutionary origin of GPBP isoforms. Our findings reveal the presence of GPBP in unicellular protists, with GPBP-2 as the most ancient isoform. In vertebrates, GPBP-1 assumed extracellular function that is further e…

ΔNp63 drives metastasis in breast cancer cells via PI3K/CD44v6 axis

2016

P63 is a transcription factor belonging to the family of p53, essential for the development and differentiation of epithelia. In recent years, it has become clear that altered expression of the different isoforms of this gene can play an important role in carcinogenesis. The p63 gene encodes for two main isoforms known as TA and ΔN p63 with different functions. The role of these different isoforms in sustaining tumor progression and metastatic spreading however has not entirely been clarified. Here we show that breast cancer initiating cells express ΔNp63 isoform that supports a more mesenchymal phenotype associated with a higher tumorigenic and metastatic potential. On the contrary, the ma…

Wnt-Dependent Oligodendroglial-Endothelial Interactions Regulate White Matter Vascularization and Attenuate Injury

2020

Recent studies have indicated oligodendroglial-vascular crosstalk during brain development, but the underlying mechanisms are incompletely understood. We report that oligodendrocyte precursor cells (OPCs) contact sprouting endothelial tip cells in mouse, ferret and human neonatal white matter. Using transgenic mice, we show that increased or decreased OPC density results in cognate changes in white matter vascular investment. Hypoxia promoted both increased OPC numbers and higher white matter vessel density, and endothelial cell expression of the Wnt pathway targets Apcdd1 and Axin2, suggesting paracrine OPC-endothelial signaling. Conditional knockout of OPC Wntless resulted in diminished w…

Piriform cortex alterations in the Ts65Dn model for down syndrome

2020

The piriform cortex is involved in olfactory information processing, that is altered in Down Syndrome. Moreover, piriform cortex has a crucial involvement in epilepsy generation and is one of the first regions affected in Alzheimer's Disease, both maladies being prevalent among Down Syndrome individuals. In this work, we studied the alterations in neuronal morphology, synaptology and structural plasticity in the piriform cortex of the Ts65Dn mouse model, which is the most used model for the study of this syndrome and mimics some of their alterations. We have observed that Ts65Dn piriform cortex displays: a reduction in dendritic arborisation, a higher density of inhibitory synapses (GAD67),…