Volume 3 of the book series Biomathematical and Biomechanical Modeling of
the Circulatory and Ventilatory Systems aims at presenting major sets of signaling
receptors mainly located at the plasma membrane, 1 in a modeling framework rather
than biological perspective. Collecting signaling effectors, their main interactions,
and major properties are the first tasks required for any modeling of cell signaling
The major objective is to comprehend the complexity of natural phenomena to
model these events. In other words, to yield the maximal amount of known information
It is our pleasure to present the Proceedings of the VI International Workshop
on Relativistic Aspects of Nuclear Physics (RANP 2000). This time,
the meeting took place in Tabatinga, a pleasant beach on the southern coast
of Brazil, for the first time out of the city of Rio de Janeiro. This series of
workshops started in 1989, aiming to stimulate Brazilian scientific activities on
Relativistic Nuclear Physics, especially among young researchers and graduate
K-Ras is a small G-protein, localized mainly at the inner leaflet of the
plasma membrane. The membrane targeting signal of this protein consists
of a polybasic C-terminal sequence of six contiguous lysines and a farnesyl-ated cysteine. Results from biophysical studies in model systems suggest
that hydrophobic and electrostatic interactions are responsible for the
membrane binding properties of K-Ras.
Caveolae are nearly ubiquitous plasma membrane domains that in adipo-cytes vary in size between 25 and 150 nm. They constitute sites of entry
into the cell as well as platforms for cell signalling. We have previously
reported that plasma membrane-associated caveolae that lack cell surface
access can be identified by electron microscopy.
It has been demonstrated that the plasma membrane expression of ZIP1 is
regulated by endocytic mechanisms. In the zinc-replete condition, the level
of surface expressed ZIP1 is low due to the rapid internalization of ZIP1.
The present study aimed to identify a sorting signal(s) in ZIP1 that medi-ated endocytosis of ZIP1.
The concentrations of two structurally distinct membrane fluidizers, the
local anesthetic benzyl alcohol (BA) and heptanol (HE), were used at con-centrations so that their addition to K562 cells caused identical increases in
the level of plasma membrane fluidity as tested by 1,6-diphenyl-1,3,5-hexa-triene (DPH) anisotropy.
Caveolae are plasma membrane invaginations with several
functions, one of which appears to be to organize receptor
mediated signalling. Here we report that in primary human
subcutaneous adipocytes the insulin receptor was localized
to caveolae by electron microscopy/immunogold detection
and by isolating caveolae from plasma membranes.
Leukocytes and other cells show an enhanced intensity of
mobile lipid in their
H NMR spectra under a variety of
conditions.Such conditions include stimulation, which has
recently been shown to involve detergent-resistant, plasma
membranedomains (DRMs)oftencalled lipidrafts.As there
ismuchspeculationsurrounding theoriginof cellularNMR-visible lipid, we analysed subcellular fractions, including
DRMs, by NMR spectroscopy.
Lipid rafts are liquid-ordered membrane microdomains with a unique protein and lipid composition found on the plasma membrane of most, if not all, mammalian cells. A large number of signalling molecules are concentrated within rafts, which have been proposed to function as signalling centres capable of facilitating eﬃcient and speciﬁc signal transduction. This review summarizes current knowledge regarding the composition, structure, and dynamic nature of lipid rafts, as well as a number of diﬀerent signalling path-
ways that are compartmentalized within these microdomains....
Subunits (a, b and c) of the interleukin-2 receptor complex (IL-2R) are involved in both proliferative and activationinduced cell death (AICD) signaling of T cells. In addition, the signaling b and c chains are shared by other cytokines (e.g. IL-7, IL-9, IL-15). However, the molecular mechanisms responsible for recruiting/sorting the a chains to the signaling chains at the cell surface are not clear.
In the current study, we report the construction of a novel system for the
detection of protein–protein interactions using yeast G-protein signaling. It
is well established that the G-protein csubunit (Gc) is anchored to the
inner leaflet of the plasma membrane via lipid modification in the C-termi-nus, and that this localization of Gcis required for signal transduction.
Elucidation of the molecular details of signal transduction through G-pro-tein coupled receptors (GPCRs) awaits the solution of high-resolution
structures of the receptor species involved in passing the extracellular infor-mation across the plasma membrane. The critical challenge in this effort is
the production of sufficient quantities of active and homogeneous receptor
species amenable to crystallization screening.
Receptors should be properly analysed in view of the microenvironment in
which they are embedded. Therefore, the concept of ‘receptosome’ was for-mulated to the complex interactions taking place between receptors and
other proteins at the plasma membrane level, and to explain very heteroge-neous or divergent cellular responses to common epigenetic factors and
modifications to the extracellular environment.
Purinergic signalling is implicated in virtually any cellular and physiological
function. These functions are mediated through the activation of different
receptor subfamilies, among which P2X receptors (P2XRs) are ligand-gated
ion channels that respond mostly to ATP.
The Tat system catalyzes the transport of folded globular
proteins across the bacterial plasma membrane and the
chloroplast thylakoid. It recognizes cleavable signal peptides
containingacritical twin-argininemotif but little isknownof
the overall structure of these peptides. In this report, we have
analyzed the secondary structure of the SufI signal peptide,
together with those of two nonfunctional variants in which
the region around the twin-arginine, RRQFI, is replaced by
KKQFI or RRQAA.
-ATPase as an energy transducing ion pump has
beenstudiedextensivelysince itsdiscovery in1957.Although
early findings suggested a role for Na
regulation of cell growth and expression of various genes,
only in recent years the mechanisms through which this
plasma membrane enzyme communicates with the nucleus
have been studied.
Several new aspects have been
highlighted: for example, a novel role for lipids as receptors which drive protein
sorting, the diversity of the sorting events that occur at the level of the Golgi
apparatus, and the cross talk between exocytosis and autophagy. Moreover, an
interesting example of how the knowledge of these pathways is exploited to generate
novel secretory routes to direct the synthesis of bio-molecules in “cell factories” is
From previous observations, addition of the antibody
raised against the α6-integrin subunit in the GC culture
medium impairs cell-spreading on LN substratum and
induces the formation of clusters of rounded cells . It
can be hypothesized that changes in cell shape might be
responsible for all or part of the functional changes
observed in survival, proliferation and steroidogenesis of
Gangliosides are glycosphingolipids mainly present at the outer leaflet of
the plasma membrane of eukaryotic cells, where they participate in recogni-tion and signalling activities. The synthesis of gangliosides is carried out in
the lumen of the Golgi apparatus by a complex system of glycosyltrans-ferases.
Selenoprotein P (SeP) is a plasma protein that contains up to 10 selenocysteine residues and accounts for about 50% of total selenium in human plasma. We have previously shown that SeP expression in the human liver cell line HepG2 is inhibited by transforming growth factor (TGF)-b1 on a transcriptional level. Smad proteins are the transcriptional mediators of TGF-b signalling and putative Smad-binding elements (SBE) comprising the core sequence CAGACA are present at two positions in the SeP promoter....