Direct protein–protein interaction between PLCγ1 and the bradykinin B2 receptor—Importance of growth conditions

The kallikrein-kinin system in health and in diseases of the kidney

Since kallikrein was discovered as a vasodilatory substance in human urine, the kallikrein-kinin system (KKS) has been considered to play a physiological role in controlling blood pressure. Gene targeting experiments in mice in which the KKS has been inactivated to varying degrees have, however, questioned this role, because basal blood pressures are not altered. Rather, these experiments have shown that the KKS has a different and important role in preventing changes associated with normal senescence in mice, and in reducing the nephropathy and accelerated senescence-associated phenotypes induced in mice by diabetes. Other experiments have shown that the KKS suppresses mitochondrial respiration, partly by nitric oxide and prostaglandins, and that this suppression may be a key to understanding how the KKS influences senescence-related diseases. Here we review the logical progression and experimental data leading to these conclusions, and discuss their relevance to human conditions.

Bradykinin modulates focal adhesions and induces stress fiber remodeling in renal papillary collecting duct cells

Focal adhesions (FAs) are specialized regions of cell attachment to the extracellular matrix. Previous works have suggested that bradykinin (BK) can modulate cell-matrix interaction. In the present study, we used a physiological cellular model to evaluate the potential role of BK in modulating FAs and stress fibers. We performed a quantitative morphometric analysis of FAs in primary cultured rat renal papillary collecting duct cells, which included size, axial ratio (shape), and average length. After 1, 5, or 10 min of incubation with BK, cultured cells were immunostained and analyzed by confocal microscopy. Although the shape of FAs was not altered, BK induced a decrease in the number of vinculin-stained FAs per cell, and a decrease in both their size and their average length, but not in talin-containing FAs, thus suggesting that BK could be inducing a restructuring of FAs. BK also induced a remodeling of the actin filament assemblies rather than their dissipation. Since we have previously demonstrated that BK stimulates activation of PLCβ in rat renal papillae, we attempted to determine whether BK can modulate FA restructuring by this mechanism, by pretreating cultured cells with the PLCβ inhibitor U73122. The present study, performed under physiological conditions with cells that were not genetically manipulated, provides new experimental evidence supporting the notion that the intrarenal hormone BK modulates FAs and actin cytoskeleton organization through a mechanism that involves the activation of PLCβ. We propose this finding as a novel mechanism for BK modulation of tubular collecting duct function.

Membranes: a meeting point for lipids, proteins and therapies

Membranes constitute a meeting point for lipids and proteins. Not only do they define the entity of cells and cytosolic organelles but they also display a wide variety of important functions previously ascribed to the activity of proteins alone. Indeed, lipids have commonly been considered a mere support for the transient or permanent association of membrane proteins, while acting as a selective cell/organelle barrier. However, mounting evidence demonstrates that lipids themselves regulate the location and activity of many membrane proteins, as well as defining membrane microdomains that serve as spatio-temporal platforms for interacting signalling proteins. Membrane lipids are crucial in the fission and fusion of lipid bilayers and they also act as sensors to control environmental or physiological conditions. Lipids and lipid structures participate directly as messengers or regulators of signal transduction. Moreover, their alteration has been associated with the development of numerous diseases. Proteins can interact with membranes through lipid co-/post-translational modifications, and electrostatic and hydrophobic interactions, van der Waals forces and hydrogen bonding are all involved in the associations among membrane proteins and lipids. The present study reviews these interactions from the molecular and biomedical point of view, and the effects of their modulation on the physiological activity of cells, the aetiology of human diseases and the design of clinical drugs. In fact, the influence of lipids on protein function is reflected in the possibility to use these molecular species as targets for therapies against cancer, obesity, neurodegenerative disorders, cardiovascular pathologies and other diseases, using a new approach called membrane-lipid therapy.

Modulation by bradykinin and nitric oxide of angiotensin II-induced apoptosis in a vascular smooth muscle cell phenotype

There is evidence for a clinical benefit of ACE inhibitors or AT1 antagonists in cardiovascular diseases with deleterious smooth muscle cells (SMC) apoptosis. We have previously shown that angiotensin II (Ang II) induces a phenotype-dependent SMC apoptosis. We asked whether bradykinin (BK) and nitric oxide (NO) could modulate Ang II-induced SMC apoptosis. BK alone did not induce significant apoptosis in either spindle (Sp-SMC) or epithelioid (Ep-SMC) SMC phenotypes cultured in serum reduction, but phenotype-dependently, reduced cell proliferation. Pretreatment with BK partly impaired Ang II-induced reduction of Ep-SMC culture viability and partly prevented apoptotic features. Pretreatment with sodium nitroprusside completely prevented all Ang II-induced deleterious effects in Ep-SMC, i. e. reduction of culture viability, Annexin V binding, nuclear condensation and cell fragmentation. These findings indicate that the BK-NO system may phenotype-dependently modulate SMC survival and in particular may oppose, mostly by NO, Ang II-induction of apoptosis in the Ep-SMC phenotype.

Roles for phosphoinositide 3-kinases, Bruton's tyrosine kinase, and Jun kinases in B lymphocyte chemotaxis and homing

B lymphocyte chemokine receptors signal to downstream effectors by activating heterotrimeric G proteins. However, many of these effectors remain unknown and the known ones often have ill-defined roles in B cell trafficking. Here we report that pharmacological inhibitors of phosphoinositide 3-kinases (wortmannin, WMN), Bruton's tyrosine kinase (LFM-A13), and Jun kinases (SP600125) all significantly impair CXCL12-induced mouse B cell chemotaxis and that of a human B lymphoma cell line. Examination of two CXCR4-induced signaling pathways revealed that LFM-A13 and WMN blocked Akt activation, while SP600125 and WMN blocked JNK activation. Each of the inhibitors impaired the homing of transferred B cells to peripheral lymph nodes. Intravital imaging of control and inhibitor-treated mouse B cells in the inguinal lymph node high endothelial venules (HEV) demonstrated a 17%, 35%, and 60% reduction in the number of firmly adherent B cells with LFM-A13, SP600125, and WMN, respectively. These results implicate chemokine receptor mediated activation of phosphoinositide 3-kinases in the firm adhesion of mouse B cells within peripheral lymph node HEV, while Bruton's tyrosine kinase and JNK activation are less important and more likely needed during B cell transmigration through the endothelium and/or trafficking into the lymph node parenchyma.

Survey of the year 2005 commercial optical biosensor literature

We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.