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Sriram Neelamegham

Publications and source records attributed to Sriram Neelamegham.

16 recordsLinked to original sources
PubMed2006

Solution structure of human von Willebrand factor studied using small angle neutron scattering.

von Willebrand factor (VWF) binding to platelets under high fluid shear is an important step regulating atherothrombosis. We applied light and small angle neutron scattering to study the solution structure of human VWF multimers and protomer. Results suggest that these proteins resemble prolate ellipsoids with radius of gyration (R(g)) of approximately 75 and approximately 30 nm for multimer and protomer, respectively. The ellipsoid dimensions/radii are 175 x 28 nm for multimers and 70 x 9.1 nm for protomers. Substructural repeat domains are evident within multimeric VWF that are indicative of elements of the protomer quarternary structure (16 nm) and individual functional domains (4.5 nm). Amino acids occupy only approximately 2% of the multimer and protomer volume, compared with 98% for serum albumin and 35% for fibrinogen. VWF treatment with guanidine.HCl, which increases VWF susceptibility to proteolysis by ADAMTS-13, causes local structural changes at length scales <10 nm without altering protein R(g). Treatment of multimer but not protomer VWF with random homobifunctional linker BS(3) prior to reduction of intermonomer disulfide linkages and Western blotting reveals a pattern of dimer and trimer units that indicate the presence of stable intermonomer non-covalent interactions within the multimer. Overall, multimeric VWF appears to be a loosely packed ellipsoidal protein with non-covalent interactions between different monomer units stabilizing its solution structure. Local, and not large scale, changes in multimer conformation are sufficient for ADAMTS-13-mediated proteolysis.

Animals↗
PubMed2006

The pattern of glycosyl- and sulfotransferase activities in cancer cell lines: a predictor of individual cancer-associated distinct carbohydrate structures for the structural identification of signature glycans.

Carbohydrate chains of cancer glycoprotein antigens contain major outer changes dictated by tissue-specific regulation of glycosyltransferase genes, the availability of sugar nucleotides, and competition between enzymes for acceptor intermediates during glycan elongation. However, it is evident from recent studies with recombinant mucin probes that the final glycosylation profiles of mucin glycoproteins are mainly determined by the cellular repertoire of glycosyltransferases. Hence, we examined various cancer cell lines for the levels of fucosyl-, beta-galactosyl, beta-N-acetylgalactosaminyl-, sialyl-, and sulfotransferase activities that generate the outer ends of the oligosaccharide chains. We have identified glycosyltransferases activities at the levels that would give rise to O-glycan chains as reported by others in breast cancer cell lines, T47D, ZR75-1, MCF-7, and MDA-MB-231. Most breast cancer cells express Gal-3-O-sulfotransferase specific for T-hapten Gal beta1-->3GalNAc alpha-, whereas the enzyme from colon cancer cells exhibits a vast preference for the Gal beta1,4GlcNAc terminal unit in O-glycans. We also studied ovarian cancer cells SW626 and PA-1 and hepatic cancer cells HepG2. Our studies show that alpha1,2-L-fucosyl-T, alpha(2,3) sialyl-T, and 3-O-Sulfo-T capable of acting on the mucin core 2 tetrasaccharide, Gal beta1,4GlcNAc beta1,6(Gal beta1,3)GalNAc alpha-, can also act on the Globo H antigen backbone, Gal beta1,3GalNAc beta1,3Gal alpha-, suggesting the existence of unique carbohydrate moieties in certain cancer-associated glycolipids. Briefly, our study indicates the following: (i) 3'-Sulfo-T-hapten has an apparent relationship to the tumorigenic potential of breast cancer cells; (ii) the 3'-sulfo Lewis(x), the 3-O-sulfo-Globo unit, and the 3-fucosylchitobiose core could be uniquely associated with colon cancer cells; (iii) synthesis of a polylactosamine chain and T-hapten are favorable in ovarian cancer cells due to negligible sialyltransferase activities; and (iv) a 6'-sialyl LacNAc unit and 3'-sialyl T-hapten appear to be prevalent structures in hepatic cancer cell glycans. Thus, it is apparent that different cancer cells are expressing unique glycan epitopes, which could be novel targets for cancer diagnosis and treatment.

Breast Neoplasms↗
PubMed2006

Quantitative measurement of selectin-ligand interactions: assays to identify a sweet pill in a library of carbohydrates.

Soluble oligosaccharides and glycoproteins can inhibit leukocyte adhesion during a range of vascular ailments including inflammation, thrombosis, and cancer metastasis. The design of such molecules in many cases is based on the structure of naturally occurring selectin ligands. In this case, synthetic selectin-ligand mimetics act as competitive inhibitors of cell adhesion. In an alternate approach, cell-permeable, small-molecule oligosaccharides have been shown to alter the metabolic pathways that lead to the biosynthesis of functional selectin-ligands. The addition of such molecules results in glycoproteins that are defective in their ability to bind selectins. Quantitative in vitro testing of the efficacy of the above inhibition strategies ideally requires the application of assays that mimic the in vivo physiological milieu in terms of the valency of selectin and selectin-ligands, the physiological fluid-flow conditions, and the use of blood cells. Assays that are performed in small volumes are preferable when the quantity of available inhibitor is scarce. Finally, the measurements must account for the rapid on- and off-rates of selectin-mediated binding interactions. This chapter addresses these issues by presenting methods to measure selectin function in enzyme-linked immunosorbent assay and flow cytometry-based static assays, cell-adhesion assays performed under shear flow in cone-plate viscometers, and Biacore surface plasmon resonance measurements of molecular-binding kinetics. Examples are presented where such methods are applied to measure the ability of simple oligosaccharides based on sialyl Lewis-X and complex molecules with the core-2 structure to block selectin function. Such methods may be extended to identify potent selectin antagonists in a library of carbohydrates.

Combinatorial Chemistry Techniques↗
PubMed2005

Biomechanics of P-selectin PSGL-1 bonds: shear threshold and integrin-independent cell adhesion.

Platelet-leukocyte adhesion may contribute to thrombosis and inflammation. We examined the heterotypic interaction between unactivated neutrophils and either thrombin receptor activating peptide (TRAP)-stimulated platelets or P-selectin-bearing beads (Ps-beads) in suspension. Cone-plate viscometers were used to apply controlled shear rates from 14 to 3000/s. Platelet-neutrophil and bead-neutrophil adhesion analysis was performed using both flow cytometry and high-speed videomicroscopy. We observed that although blocking antibodies against either P-selectin or P-selectin glycoprotein ligand-1 (PSGL-1) alone inhibited platelet-neutrophil adhesion by approximately 60% at 140/s, these reagents completely blocked adhesion at 3000/s. Anti-Mac-1 alone did not alter platelet-neutrophil adhesion rates at any shear rate, though in synergy with selectin antagonists it abrogated cell binding. Unstimulated neutrophils avidly bound Ps-beads and activated platelets in an integrin-independent manner, suggesting that purely selectin-dependent cell adhesion is possible. In support of this, antagonists against P-selectin or PSGL-1 caused dissociation of previously formed platelet-neutrophil and Ps-bead neutrophil aggregates under shear in a variety of experimental systems, including in assays performed with whole blood. In studies where medium viscosity and shear rate were varied, a shear threshold for P-selectin PSGL-1 binding was also noted at shear rates <100/s when Ps-beads collided with isolated neutrophils. Results are discussed in light of biophysical computations that characterize the collision between unequal-size particles in linear shear flow. Overall, our studies reveal an integrin-independent regime for cell adhesion and weak shear threshold for P-selectin PSGL-1 interactions that may be physiologically relevant.

Binding Sites↗
PubMed2005

Analysis of the specificity of sialyltransferases toward mucin core 2, globo, and related structures. identification of the sialylation sequence and the effects of sulfate, fucose, methyl, and fluoro substituents of the carbohydrate chain in the biosynthesis of selectin and siglec ligands, and novel sialylation by cloned alpha2,3(O)sialyltransferase.

Sialic acids are key determinants in many carbohydrates involved in biological recognition. We studied the acceptor specificities of three cloned sialyltransferases (STs) [alpha2,3(N)ST, alpha2,3(O)ST, and alpha2,6(N)ST] and another alpha2,3(O)ST present in prostate cancer cell LNCaP toward mucin core 2 tetrasaccharide [Galbeta1,4GlcNAcbeta1,6(Galbeta1,3)GalNAcalpha-O-Bn] and Globo [Galbeta1,3GalNAcbeta1,3Galalpha-O-Me] structures containing sialyl, fucosyl, sulfo, methyl, or fluoro substituents by identifying the products by electrospray ionization tandem mass spectral analysis and other biochemical methods. The Globo precursor was an efficient acceptor for both alpha2,3(N)ST and alpha2,3(O)ST, whereas only alpha2,3(O)ST used its deoxy analogue (d-Fucbeta1,3GalNAcbeta1,3-Gal-alpha-O-Me); 2-O-MeGalbeta1,3GlcNAc and 4-OMeGalbeta1,4GlcNAc were specific acceptors for alpha2,3(N)ST. Other major findings of this study include: (i) alpha2,3 sialylation of beta1,3Gal in mucin core 2 can proceed even after alpha1,3 fucosylation of beta1,6-linked LacNAc. (ii) Sialylation of beta1,3Gal must precede the sialylation of beta1,4Gal for favorable biosynthesis of mucin core 2 compounds. (iii) alpha2,3 sialylation of the 6-O-sulfoLacNAc moiety in mucin core 2 (e.g., GlyCAM-1) is facilitated when beta1,3Gal has already been alpha2,3 sialylated. (iv) alpha2,6(N)ST was absolutely specific for the beta1,4Gal in mucin core 2. Either alpha1,3 fucosylation or 6-O-sulfation of the GlcNAc moiety reduced the activity. Sialylation of beta1,3Gal in addition to 6-O-sulfation of GlcNAc moiety abolished the activity. (v) Prior alpha2,3 sialylation or 3-O-sulfation of beta1,3Gal would not affect alpha2,6 sialylation of Galbeta1,4GlcNAc of mucin core 2. (vi) A 3- or 4-fluoro substituent in beta1,4Gal resulted in poor acceptors for the cloned alpha2,6(N)ST and alpha2,3(N)ST, whereas 4-fluoro- or 4-OMe-Galbeta1,3GalNAcalpha was a good acceptor for cloned alpha2,3(O)ST. (vii) 4-O-Methylation of beta1,4Gal abolished the acceptor ability toward alpha2,6(N)ST but increased the acceptor efficiency considerably toward alpha2,3(N)ST. (viii) Just like LNCaPalpha1,2-FT and Gal-3-O-sulfotransferase T2, the cloned alpha2,3(N)ST which modifies terminal Gal in Galbeta1,4GlcNAc also efficiently utilizes the terminal beta1,3Gal in the Globo backbone. Utilization of C-3 blocked compounds such as 3-O-sulfo-Galbeta1,3GalNAcbeta1,3Galalpha-OMe as acceptors by cloned alpha2,3(O)ST and analyses of the resulting products by lectin chromatography and mass spectrometry indicate that alpha2,3(O)ST is capable of attaching NeuAc to another position in C-3-substituted beta1,3Gal.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed2005

Affinity and kinetics of sialyl Lewis-X and core-2 based oligosaccharides binding to L- and P-selectin.

Soluble oligosaccharide mimetics of natural selectin ligands act as competitive inhibitors of leukocyte adhesion in models of inflammation. We quantified the binding of simple oligosaccharides based on sialyl Lewis-X (sLe(X)) and complex molecules with the core-2 structure to L- and P-selectin, under both static and fluid flow conditions. Isolated human neutrophils were employed to mimic the physiological valency of selectins and selectin ligands. Surface plasmon resonance studies quantified binding kinetics. We observed the following: (i) The functional group at the anomeric position of carbohydrates plays an important role during selectin recognition, since sLe(X) and sialyl Lewis-a (sLe(a)) were approximately 5-7-fold poorer inhibitors of L-selectin mediated cell adhesion compared to their methyl glycosides. (ii) Despite their homology to physiological glycans, the putative carbohydrate epitopes of GlyCAM-1 and PSGL-1 bound selectins with low affinity comparable to that of sLe(X)-selectin interactions. Thus, besides the carbohydrate portion, the protein core of GlyCAM-1 or the presentation of carbohydrates in clusters on this glycoprotein may contribute to selectin recognition. (iii) A compound Galbeta1,4(Fucalpha1,3)GlcNAcbeta1,6(GalNAcbeta1,3)GalNAcalpha-OMe was identified which blocked L- and P-selectin binding at 30-100-fold lower doses than sLe(X). (iv) Surface plasmon resonance experiments determined that an sLe(X) analogue (TBC1269) competitively inhibited, via steric/allosteric mechanisms, the binding of two anti-P-selectin function blocking antibodies that recognized different epitopes of P-selectin. (v) TBC1269 bound P-selectin via both calcium-dependent and -independent mechanisms, with K(D) of approximately 111.4 microM. The measured on- and off-rates were high (k(off) > 3 s(-)(1), k(on) > 27,000 M(-)(1) s(-)(1)). Similar binding kinetics are expected for sLe(X)-selectin interactions. Taken together, our study provides new insight into the kinetics and mechanisms of carbohydrate interaction with selectins.

Animals↗
PubMed2004

Sensitivity, principal component and flux analysis applied to signal transduction: the case of epidermal growth factor mediated signaling.

MOTIVATION: Novel high-throughput genomic and proteomic tools are allowing the integration of information from a range of biological assays into a single conceptual framework. This framework is often described as a network of biochemical reactions. We present strategies for the analysis of such networks. RESULTS: The direct differential method is described for the systematic evaluation of scaled sensitivity coefficients in reaction networks. Principal component analysis, based on an eigenvalue-eigenvector analysis of the scaled sensitivity coefficient matrix, is applied to rank individual reactions in the network based on their effect on system output. When combined with flux analysis, sensitivity analysis allows model reduction or simplification. Using epidermal growth factor (EGF) mediated signaling and trafficking as an example of signal transduction, we demonstrate that sensitivity analysis quantitatively reveals the dependence of dual-phosphorylated extracellular signal-regulated kinase (ERK) concentration on individual reaction rate constants. It predicts that EGF mediated reactions proceed primarily via an Shc-dependent pathway. Further, it suggests that receptor internalization and endosomal signaling are important features regulating signal output only at low EGF dosages and at later times.

Algorithms↗
PubMed2004

Hydrodynamic forces applied on intercellular bonds, soluble molecules, and cell-surface receptors.

Cells and biomolecules exposed to blood circulation experience hydrodynamic forces that affect their function. We present a methodology to estimate fluid forces and force loading rates applied on cellular aggregates, cell-surface proteins, and soluble molecules. Low Reynolds-number hydrodynamic theory is employed. Selected results are presented for biological cases involving platelets, neutrophils, tumor cells, GpIb-like cell-surface receptors, and plasma von Willebrand factor (vWF)-like soluble proteins. Calculations reveal the following: 1), upon application of constant linear shear, cell aggregates and biomolecules experience time-varying forces due to their tumbling motion. 2), In comparison to neutrophil homotypic aggregates, the maximum force applied on neutrophil-platelet aggregates is approximately threefold lower. Thus, alterations in cell size may dramatically alter adhesion molecule requirement for efficient cell binding. Whereas peak forces on homotypic cell doublets are tensile, shear forces dominate in heterotypic doublets with radius ratio <0.3. 3), The peak forces on platelet GpIb and von Willebrand factor are of comparable magnitude. However, they are orders-of-magnitude lower than those applied on intercellular bonds. Charts are provided to rapidly evaluate the magnitude of hydrodynamic force and rotation time-period occurring in any given experiment. The calculation scheme may find application in studies of vascular biology and receptor biophysics.

Blood Platelets↗
PubMed2004

Cooperativity between selectins and beta2-integrins define neutrophil capture and stable adhesion in shear flow.

A cooperative, sequential process of molecular recognition governs leukocyte capture, rolling, and arrest on inflamed endothelium. Flowing neutrophils are captured via heterotypic adhesive interactions mediated by endothelial E-selectin, whereas homotypic interactions between neutrophils are mediated by L-selectin. To elucidate how each selectin facilitates the transition to CD18-mediated stable adhesion, E-selectin and L-selectin were expressed at defined site density in a murine pre-B-cell line. Direct observation of two-body collisions revealed that 30% of neutrophil interactions with E-selectin transfectants formed doublets at low shear rate G = 14 s(-1) whereas a threshold shear rate 14 s(-1) < or = G < or = 10 s(-1) was necessary for L-selectin adhesion. Adhesion via L-selectin resisted rupture at high shear stress, while E-selectin tethered doublets remained intact longer once formed. Moreover, higher expression of L-selectin (1100 sites/microm2) than that of E-selectin (220 sites/microm2) was required for comparable heterotypic adhesion efficiency. With a threefold rise in active CD18 upregulated on chemotactically stimulated neutrophils, homotypic adhesion efficiency increased 10-fold compared to less than 5-fold for heterotypic adhesion to selectin transfectants. Co-expression of E-selectin and ICAM-1 boosted adhesion efficiency threefold more than either receptor alone over the range of active CD18 expression. These data are the first to quantify adhesion efficiency mediated by selectin tethering and conformational activation of beta2-integrin in neutrophils in shear flow.

Animals↗
PubMed2003

Identification of physiologically relevant substrates for cloned Gal: 3-O-sulfotransferases (Gal3STs): distinct high affinity of Gal3ST-2 and LS180 sulfotransferase for the globo H backbone, Gal3ST-3 for N-glycan multiterminal Galbeta1, 4GlcNAcbeta units and 6-sulfoGalbeta1, 4GlcNAcbeta, and Gal3ST-4 for the mucin core-2 trisaccharide.

Sulfated glycoconjugates regulate biological processes such as cell adhesion and cancer metastasis. We examined the acceptor specificities and kinetic properties of three cloned Gal:3-O-sulfotransferases (Gal3STs) ST-2, ST-3, and ST-4 along with a purified Gal3ST from colon carcinoma LS180 cells. Gal3ST-2 was the dominant Gal3ST in LS180. While the mucin core-2 structure Galbeta1,4GlcNAcbeta1,6(3-O-MeGalbeta1,3)GalNAcalpha-O-Bn (where Bn is benzyl) and the disaccharide Galbeta1,4GlcNAc served as high affinity acceptors for Gal3ST-2 and Gal3ST-3, 3-O-MeGalbeta1,4GlcNAcbeta1,-6(Galbeta1,3)GalNAcalpha-O-Bn and Galbeta1,3GalNAcalpha-O-Al (where Al is allyl) were efficient acceptors for Gal3ST-4. The activities of Gal3ST-2 and Gal3ST-3 could be distinguished with the Globo H precursor (Galbeta1,3GalNAcbeta1,3Galalpha-O-Me) and fetuin triantennary asialoglycopeptide. Gal3ST-2 acted efficiently on the former, while Gal3ST-3 showed preference for the latter. Gal3ST-4 also acted on the Globo H precursor but not the glycopeptide. In support of the specificity, Gal3ST-2 activity toward the Galbeta1,4GlcNAcbeta unit on mucin core-2 as well as the Globo H precursor could be inhibited competitively by Galbeta1,4GlcNAcbeta1,6(3-O-sulfoGalbeta1,3)GalNAcalpha-O-Bn but not 3-O-sulfoGalbeta1,-4GlcNAcbeta1,6(Galbeta1,3)GalNAcalpha-O-Bn. Remarkably these sulfotransferases were uniquely specific for sulfated substrates: Gal3ST-3 utilized Galbeta1,4(6-O-sulfo)-GlcNAcbeta-O-Al as acceptor, Gal3ST-2 acted efficiently on Galbeta1,3(6-O-sulfo)GlcNAcbeta-O-Al, and Gal3ST-4 acted efficiently on Galbeta1,3(6-O-sulfo)GalNAcalpha-O-Al. Mg(2+), Mn(2+), and Ca(2+) stimulated the activities of Gal3ST-2, whereas only Mg(2+) augmented Gal3ST-3 activity. Divalent cations did not stimulate Gal3ST-4, although inhibition was noted at high Mn(2+) concentrations. The fine substrate specificities of Gal3STs indicate a distinct physiological role for each enzyme.

Acetylglucosamine↗
PubMed2003

An analysis tool to quantify the efficiency of cell tethering and firm-adhesion in the parallel-plate flow chamber.

The parallel-plate flow chamber is applied in immunological studies to quantify the adhesivity of cells (e.g. leukocytes) onto ligand-bearing substrates (e.g. endothelial cells) under fluid-flow conditions that mimic the human vasculature. It is also applied to quantify platelet adhesion in vascular injury models, and tumor cell adhesion in models of cancer metastasis. Typical measures of cell adhesion in this setup include the rolling and adherent cell density. These measures are functions of not only the cellular adhesivity, but also of the physical features of the experimental system (e.g. inlet cell concentration) and observation time. Here, we present a mathematical model to better analyze experimental data on cell rolling, firm-arrest and transmigration. The overall goal is to quantify the biological adhesivity of cells independent of the physical parameters that control the rate of cell-substrate and cell-cell collision. This analysis yields four independent parameters: Primary capture frequency quantifies the rate at which cells in the free stream initiate rolling. Firm-arrest frequency is a measure of the transition from rolling to firm-binding. These two frequency parameters are inversely proportional to the distance the average cell convects in the free stream adjacent to the substrate before tethering, or rolls on the substrate before firm-adhesion, respectively. Rolling-release frequency is introduced to quantify the reversible release of cells from rolling back into the free stream. Finally, cell-cell capture probability quantifies the fraction of collisions between cells in free stream and recruited substrate-bound cells that result in tethering. The proposed analysis methodology may find application in studies of inflammation, thrombosis and cancer research.

Cell Adhesion↗
PubMed2002

Aspects of hydrodynamic shear regulating shear-induced platelet activation and self-association of von Willebrand factor in suspension.

The binding of plasma von Willebrand factor (VWF) to platelet receptor GpIb under high hydrodynamic shear leads to platelet activation and subsequent shear-induced platelet aggregation (SIPA). We quantitatively examined the aspects of fluid flow that regulate platelet activation by subjecting human blood and isolated platelets to well-defined shear conditions in a cone-plate viscometer. We made the following observations. First, Annexin V binding to phosphatidyl serine expressed on activated cells was detectable within 10 seconds of shear application. Second, fluid shear stress rather than shear rate controls platelet activation, and a threshold shear stress of approximately 80 dyn/cm(2) is necessary to induce significant activation. Under these conditions, individual domains of soluble VWF and platelet GpIb are subjected to similar magnitudes of fluid forces on the order of 0.1 pN, whereas GpIb with bound VWF is subjected to 1 pN. Third, cell-cell collisions and time-varying stresses are not essential for platelet activation. Fourth, the mechanism of platelet activation can be resolved in 2 steps based on the contribution of VWF and fluid forces. Fluid shear and VWF are required during the first step, when GpIb-VWF binding likely occurs. Subsequently, high shear forces alone in the absence of VWF in suspension can induce platelet activation. In other experiments, purified VWF was subjected to shear in the viscometer, and VWF morphology was assessed using light scattering. These studies demonstrate, for the first time, the ability of hydrodynamic forces to induce VWF aggregation in suspension. This VWF self-association may be an additional feature involved in controlling cell adhesion rates in circulation.

Annexin A5↗
PubMed2002

Estimating the efficiency of cell capture and arrest in flow chambers: study of neutrophil binding via E-selectin and ICAM-1.

A mathematical model was developed to quantify the efficiency of cell-substrate attachment in the parallel-plate flow chamber. The model decouples the physical features of the system that affect cell-substrate collision rates from the biological features that influence cellular adhesivity. Thus, experimental data on cell rolling and adhesion density are converted into "frequency" parameters that quantify the "efficiency" with which cells in the flow chamber progress from the free stream to rolling, and transition from rolling to firm arrest. The model was partially validated by comparing simulation results with experiments where neutrophils rolled and adhered onto substrates composed of cotransfected cells bearing E-selectin and intercellular adhesion molecule-1 (ICAM-1). Results suggest that: 1) Neutrophils contact the E-selectin substrate on average for 4-8.5s before tethering. This contact duration is insensitive to applied shear stress. 2) At 2 dyn/cm(2), approximately 28% of the collisions between the cells and substrate result in primary capture. Also, approximately 5-7% of collisions between neutrophils in the free stream and previously recruited neutrophils bound on the substrate result in secondary capture. These percentages were higher at lower shears. 3) An adherent cell may influence the flow streams in its vicinity up to a distance of 2.5 cell diameters away. 4) Our estimates of selectin on-rate in cellular systems compare favorably with data from reconstituted systems with immobilized soluble E-selectin. In magnitude, the observed on-rates occur in the order, L-selectin > P-selectin > E-selectin.

Algorithms↗
PubMedDate not supplied

Transport features, reaction kinetics and receptor biomechanics controlling selectin and integrin mediated cell adhesion.

The distinct and overlapping roles of adhesion molecules belonging to the selectin and integrin families control the rate of leukocyte adhesion to stimulated vascular endothelial cells under hydrodynamic shear flow. Crystal structures have appeared for some of these interactions which complement molecular biology experiments, and clarify the molecular mechanism of the receptor-ligand binding interactions. Binding affinity data have also appeared using surface plasmon resonance and single-molecule biophysics experiments. These studies confirm and extend the predictions of previous experiments carried out in parallel-plate flow chambers, and cone and plate viscometers. This review discusses the current state of understanding on how molecular bond formation rates coupled with cellular and hydrodynamic features regulate leukocyte binding to endothelial cells.

Binding Sites↗