glycyl-arginyl-glycyl-glutamyl-seryl-proline and arginyl-glycyl-aspartic-acid

In our studies of VLA-3 we have shown (i) that a single integrin (VLA-3) can bind to multiple ligands by different mechanisms, involving RGD and non-RGD sites, which are regulated differently by divalent cations. Also we showed from the primary sequence of VLA-3 that it is only distantly related to the other cleaved alpha subunits. In our studies of VLA-2 we have shown that a single integrin may have at least three functional forms, depending on the cell type where expressed. In addition, we have expressed functional VLA-2 in RD cells, resulting in both Coll and Lm binding functions in vitro, and increased tumor cell metastasis in vivo in nude mice.

Topics: Amino Acid Sequence; Animals; Binding, Competitive; Cations, Divalent; Cell Adhesion; Collagen; Fibronectins; Humans; Laminin; Ligands; Mice; Mice, Nude; Molecular Sequence Data; Neoplasm Proteins; Oligopeptides; Protein Conformation; Receptors, Cell Surface; Receptors, Collagen; Receptors, Fibronectin; Receptors, Immunologic; Receptors, Laminin; Receptors, Peptide; Receptors, Very Late Antigen; Recombinant Proteins; Tumor Cells, Cultured

The study of implantation has been facilitated by the identification of specific biomarkers that are associated with uterine receptivity. The alpha(v)beta(3) integrin is a cell surface adhesion receptor, whose expression has been shown to be elevated in the endometrium at the time of implantation in both humans and other mammalian species; however, the distribution of alpha(v)beta(3) in the rabbit model is unknown. The rabbit has been shown to be an excellent model for the study of implantation. As an obligate ovulator, the timing of pregnancy can be precisely established, and embryonic attachment occurs through specialized trophoblast-endometrial structures known as trophoblastic knobs. In the present study, the expression of alpha(v)beta(3) integrin subunit in the rabbit uterus was examined by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and in situ hybridization. Expression of the alpha(v)beta(3) integrin was examined in Day 6.5 embryos, flushed from pregnant does. Immunofluorescence demonstrated strong immunostaining on the rabbit blastocyst (Day 6.5). RT-PCR analyses showed higher levels of mRNA for beta(3) subunit at the implantation site, with reduced expression in nonimplantation sites and in nonpregnant adult and immature endometrium. Immunohistochemistry demonstrated little, if any, beta(3) immunoreactivity on the endometrial epithelium. In contrast, in situ hybridization showed expression of the beta(3) integrin subunit mRNA in the uterine myometrium and on the trophoblast. To further determine the functional significance of alpha(v)beta(3) integrin expression during implantation, pregnant female rabbits that underwent ventral laparotomy on the morning of Day 6 received intrauterine injection of the following into the right uterine horn: 1) the monoclonal alpha(v)beta(3) neutralizing antibody (LM609), 2) arg-gly-asp (RGD) hexapeptides (GRGDSP), 3) non-RGD hexapeptides (GRGESP), and 4) IgG isotype matched control antibody. The left horn served as a control and received only saline injections. A significant reduction in the number of implantation sites was observed in the horns receiving anti-alpha(v)beta(3) antibody (P < 0.001) and the RGD peptides (P = 0.03). In the rabbit, the alpha(v)beta(3) integrin is present on the embryo and trophoblast and appears to be involved in early embryo-maternal interaction.

Topics: Animals; Embryo Implantation; Endometrium; Female; Immunohistochemistry; In Situ Hybridization; Integrin alphaVbeta3; Male; Oligopeptides; Pregnancy; Rabbits; Reverse Transcriptase Polymerase Chain Reaction

Beta ig-h3 is a transforming growth factor-beta (TGF-beta)-induced cell-adhesive molecule and has an RGD sequence at its C-terminus. A previous report suggested that beta ig-h3 normally undergoes carboxy-terminal processing that results in the loss of the RGD sequence. RGD peptides appear to play various roles in cell function. Here we show that the RGD peptides released from beta ig-h3 may facilitate TGF-beta-induced apoptosis. We found that carboxy-terminal cleavage of beta ig-h3 occurred after its secretion, and that overexpression of the wild-type beta ig-h3 induced apoptosis, unlike the C-terminal deleted but RGD-containing mutant beta ig-h3, which is resistant to C-terminal processing. The beta ig-h3-induced apoptosis was abolished by either deletion of the RGD sequence or mutation of RGD to RAE. Synthetic peptides of ERGDEL and GRGDSP derived from beta ig-h3 and fibronectin, respectively, also induced apoptosis, unlike ERGEEL and GRGESP. Culture supernatants of cells overexpressing beta ig-h3 filtered to isolate molecules smaller than 3 kDa also induced apoptosis. A fusion protein composed of the N-terminal 100 amino acids of fibronectin and the RGD-containing C-terminal part of beta ig-h3 was also subjected to C-terminal cleavage and overexpression resulted in apoptosis. The anti-beta ig-h3 antibody blocks TGF-beta-induced apoptosis. Thus, beta ig-h3 may be important in regulating cell apoptosis by providing soluble RGD peptides.

Topics: Amino Acid Motifs; Animals; Antibodies, Monoclonal; Apoptosis; Cell Adhesion; CHO Cells; Cricetinae; Cricetulus; Extracellular Matrix Proteins; Fibronectins; Humans; Monensin; Neoplasm Proteins; Oligopeptides; Peptide Fragments; Protein Processing, Post-Translational; Protein Sorting Signals; Recombinant Fusion Proteins; Sequence Deletion; Transfection; Transforming Growth Factor beta

Inhibition of autophagic proteolysis by hypoosmotic or amino acid-induced hepatocyte swelling requires osmosignaling toward p38MAPK; however, the upstream osmosensing and signaling events are unknown. These were studied in the intact perfused rat liver with a preserved in situ environment of hepatocytes. It was found that hypoosmotic hepatocyte swelling led to an activation of Src (but not FAK), Erks, and p38MAPK, which was prevented by the integrin inhibitory hexapeptide GRGDSP, but not its inactive analogue GRGESP. Src inhibition by PP-2 prevented hypoosmotic MAP kinase activation, indicating that the integrin/Src system is located upstream in the osmosignaling toward p38MAPK and Erks. Inhibition of the integrin/Src system by the RGD motif-containing peptide or PP-2 also prevented the inhibition of proteolysis and the decrease in autophagic vacuole volume, which is otherwise observed in response to hypoosmotic or glutamine/glycine-induced hepatocyte swelling. These inhibitors, however, did not affect swelling-independent proteolysis inhibition by phenylalanine. In line with a role of p38MAPK in triggering the volume regulatory decrease (RVD), PP-2 and the RGD peptide blunted RVD in response to hypoosmotic cell swelling. The data identify integrins and Src as upstream events in the osmosignaling toward MAP kinases, proteolysis, and RVD. They further point to a role of integrins as osmo- and mechanosensors in the intact liver, which may provide a link between cell volume and cell function.

Topics: Animals; Autophagy; Cell Size; Cells, Cultured; Hepatocytes; In Vitro Techniques; Integrins; Liver; Male; MAP Kinase Signaling System; Mitogen-Activated Protein Kinases; Models, Biological; Oligopeptides; p38 Mitogen-Activated Protein Kinases; Perfusion; Rats; Rats, Wistar; Signal Transduction; src-Family Kinases; Water-Electrolyte Balance

The expression of integrin vitronectin (VN) receptors on Candida albicans yeasts and their involvement in the adhesion to VN were investigated. By immunofluorescence and cytofluorimetric analysis, several antibodies directed against human alphav, beta3, beta5, alphavbeta3, or alphavbeta5 integrin positively stained C. albicans yeasts. Biochemical analysis on yeast lysates with anti-human alphav, beta3, or beta5 antibody revealed molecular species of 130, 110, 100, and 84 kDa. The 130-kDa band was identified as alphav, whereas the doublet of 110/100 kDa and the 84-kDa band likely correspond to the beta3 and beta5 subunits, respectively. Some 48%-54% of Candida yeasts specifically adhered to VN, and this binding was strongly inhibited by anti-human alphav, beta3, alphavbeta3, and alphavbeta5 antibodies and by RGD- but not RGE-containing peptides. In addition, VN inhibited C. albicans adherence to a human endothelial cell line. Thus, C. albicans in the yeast phase expresses VN receptors antigenically related to the vertebrate alphavbeta3 and alphavbeta5 integrins, which mediate its adhesion to VN.

Topics: Candida albicans; Cations, Divalent; Cell Adhesion; Cell Adhesion Molecules; Humans; Integrins; Oligopeptides; Protein Binding; Receptors, Vitronectin; Vitronectin

A novel protein was engineered by inserting the GRGDS motif of fibronectin within the 14-residue loop of the EGF-like module from human complement protease C1r. The resulting chimeric EGF-RGD module (52 residues, three disulfide bridges) was assembled by automated solid-phase synthesis using the t-Boc strategy. Using reduced/oxidized glutathione, the EGF-RGD module was folded as efficiently as the natural C1r-EGF module, resulting in formation of the appropriate disulfide bridge pattern as shown by mass spectrometry and N-terminal sequence analyses of thermolytic fragments. Circular dichroism and NMR measurements provided further indication that introduction of the GRGDS motif had no significant effect on the folding. Using Chinese Hamster Ovary (CHO) cells bearing the integrin receptors specific for fibronectin and vitronectin, EGF-RGD was shown to induce cell adhesion via the introduced GRGDS motif. Cell binding was inhibited specifically and efficiently by the synthetic peptide GRGDSP and by fibronectin, and to a much lesser extent by vitronectin, whereas the monoclonal antibody PB1 directed to the alpha5 subunit of alpha5beta1 integrin had no effect. The ability of EGF-RGD to trigger significant cell spreading and intracellular signaling was also demonstrated using immunofluorescence and confocal microscopy.

Topics: Amino Acid Sequence; Animals; Binding, Competitive; Cell Adhesion; CHO Cells; Circular Dichroism; Complement C1r; Cricetinae; Epidermal Growth Factor; Fibronectins; Fluorescent Antibody Technique; Mass Spectrometry; Models, Molecular; Molecular Sequence Data; Oligopeptides; Recombinant Fusion Proteins; Sequence Analysis

Fibrinogen and fibrin mediate the adhesion of many cell types. In this report, the adhesion sites for human dermal fibroblasts on fibrinogen are identified and characterized. Fibroblasts showed a time- and dose-dependent adhesion to fibrinogen. Using a combination of synthetic peptide mimetics, monoclonal antibodies, and recombinant fibrinogens, two major classes of adhesive sites were identified. One class was RGD-dependent and involved the RGD sites in the alpha chain of fibrinogen. alpha V integrins present on fibroblasts appeared to mediate this adhesion. Inhibition studies showed that the RGD-independent site was blocked by an ICAM-1 antagonist peptide. Furthermore, the inhibition was additive with RGD peptide inhibition and accounted for essentially all of the fibroblast adhesion. Together, these results suggest that fibroblast adhesion to fibrinogen is mediated by both alpha V integrins and ICAM-1.

Topics: Amino Acid Sequence; Cell Adhesion; Cells, Cultured; Fibrinogen; Fibroblasts; Humans; Infant, Newborn; Kinetics; Male; Oligopeptides; Recombinant Proteins; Skin; Skin Physiological Phenomena

Fibronectin (Fn) is a multifunctional adhesive protein found on cell surfaces as well as in plasma. It is also believed to play an important role in bacterial adherence to host tissues. Molecular analyses of Fn have shown that the amino acid triplet arginine-glycine-aspartic acid (RGD) sequence functions as a binding site. We examined the role of the RGD sequence on bacterial adherence to Fn. The pretreatment of Streptococcus mitis with synthetic RGD-containing peptide reduced the number of bound bacteria to the Fn coated plates by 76%. In contrast, a control peptide containing the RGE sequence showed no inhibition. These data indicate that synthetic RGD peptides may be useful for the inhibition of bacterial adherence to Fn on host cell surfaces.

Topics: Amino Acid Sequence; Bacterial Adhesion; Binding Sites; Fibrinogen; Fibronectins; Oligopeptides; Platelet Aggregation Inhibitors; Receptors, Immunologic; Streptococcus

The potential role of integrins in the myogenic mechanism was studied in the rat afferent arteriole (AA) by fluorescence immunolocalization and microperfusion of isolated AA. Confocal fluorescence images were acquired from frozen sections of rat kidney after indirect immunostaining for various integrin beta- and alpha-subunits. The beta 1-, beta 3-, alpha 3-, alpha 5-, and alpha V-integrins were found on the plasma membrane in smooth muscle of AA, providing the morphological basis for participation of integrins in mechanotransduction. With 1 mM nitro-L-arginine methyl ester (L-NAME) in the luminal perfusate to inhibit endogenous nitric oxide (NO) production from AA, the hexapeptide GRGDSP (10(-7)-10(-3)M) induced immediate vasoconstriction. The constriction was dose dependent and specific or peptides with arginine-glycine-aspartic acid (RGD) motifs, commonly found on the binding sites of extracellular matrix to integrins. In controls, the hexapeptide GRGESP induced no constriction. GRGDSP, 1 mM, induced a 21.6 +/- 2.6% decrease (P < 0.05, n = 6) in lumen diameter for 30 s and an 18.3 +/- 4.1% increase (P < 0.05, n = 6) in smooth muscle intracellular calcium concentration for 18 s, as measured by the emission ratio of Fluo-3/Fura Red. Binding of exogenous RGD motifs with exposed integrins on AA smooth muscle therefore triggers calcium-dependent vasoconstriction. However, the dose response to RGD was not sensitive to the myogenic tone of the vessel, which suggests that the integrin-mediated vasoconstriction is different from myogenic constriction.

Topics: Amino Acid Sequence; Animals; Antigens, CD; Arterioles; Calcium; Cell Size; Integrin alpha3; Integrin alpha5; Integrin alphaV; Integrin beta1; Integrin beta3; Integrins; Kidney; Male; Muscle, Smooth, Vascular; Nephrons; NG-Nitroarginine Methyl Ester; Oligopeptides; Peptides, Cyclic; Platelet Membrane Glycoproteins; Rats; Rats, Sprague-Dawley; Renal Circulation; Structure-Activity Relationship; Vasoconstriction

We have investigated the expression and localization of fibronectin, laminin, and their receptors, and we used an in vitro chick chondrocyte differentiation model to define a time hierarchy for their appearance in early chondro-genesis and to determine their role in the cell condensation process. By serum fibronectin depletion/reconstitution, or GRGDSP peptide competition experiments, we show that fibronectin contributes to the initial cell-cell interactions that occur during condensation. In later stages, a down-regulation of both fibronectin and of its alpha5beta1 integrin receptor occur, as demonstrated by mRNA and protein kinetics. Immunolocalisation studies suggest that the reduction of fibronectin in discrete areas is involved in local activation of the cell differentiation program. Furthermore, we show that laminin is expressed during the in vitro cell condensation process in areas that are negative for fibronectin staining. The types of laminin as well as the timing of expression have been determined by northern blot and RT-PCR analyses. The highest levels of expression are coincident with maximal cell aggregation. The alpha3beta1 laminin receptor, highly expressed in dedifferentiated cells, follows later on the ligand trend. During in vitro chondrogenesis, a down-regulation in the B isoform, and an up-regulation of the A isoform, of the alpha subunit of the alpha6beta1 laminin receptor occurs. Immunolocalisation studies suggest that laminin is involved in the definition of differentiating areas as opposed to non differentiating areas of the condensed region, i.e. the periphery, which eventually gives rise to the perichondrium.

Topics: Animals; Antibody Specificity; Cell Adhesion; Cell Differentiation; Cells, Cultured; Chick Embryo; Chondrocytes; Down-Regulation; Extracellular Matrix Proteins; Fibronectins; Gene Expression Regulation, Developmental; Integrins; Laminin; Limb Buds; Oligopeptides; Receptors, Laminin; RNA, Messenger; Tibia

Loss of fibronectin (FN) from the cell surface has been shown to be closely associated with malignant transformation of cells. To elucidate the role of the FN matrix in the modulation of malignant phenotypes, we overexpressed a full-length cDNA encoding plasma-type FN in HT1080 human fibrosarcoma cells. The cells overexpressing FN adopted a more flattened morphology and deposited a moderately developed FN matrix both in vitro and in vivo, although the level of expression of integrin alpha5beta1 remained unchanged. FN-overexpressing cells exhibited a reduced cell motility on the substratum and grew poorly when injected s.c. into nude mice. Overexpression of FN also suppressed the ability of the tumor cells to proliferate in soft agar, whereas the suppression was reversed by inclusion in soft agar of the Arg-Gly-Asp (RGD)-containing peptide and adhesion-blocking antibodies against the central cell-binding domain of FN. Neither cell motility nor growth potential was altered by overexpression of a truncated form of FN lacking the central cell-binding domain. These results, taken together, indicate that increased deposition of FN in the pericellular matrix per se can suppress the motility and growth potential of tumor cells through interaction with RGD-recognizing integrins, most likely alpha5beta1.

Topics: Animals; Cell Adhesion; Cell Division; DNA, Complementary; Female; Fibronectins; Fibrosarcoma; Gene Expression Regulation, Neoplastic; Humans; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Transplantation; Oligopeptides; Peptide Fragments; Phenotype; Receptors, Fibronectin; Recombinant Fusion Proteins; Transfection; Tumor Stem Cell Assay

Adherence to cells and matrices participates in lymphocyte migration and tissue localization and contributes to the regulation of growth and differentiation of the lymphoid cells. The adherence is mainly mediated by three families of cell-surface proteins: integrins, immunoglobulin (Ig)-related molecules, and selectins. Integrins recognize Ig-related molecules such as ICAMs as well as fibronectin (FN), vitronectin (VN), and other matrix proteins. In this study, the in vitro adhesive properties of two Epstein-Barr virus-carrying B lymphoblastoid cell lines, IB-4 and NAD-20, were compared. IB-4 cells grow as a monolayer in contrast to NAD-20 cells, which grow as cell clusters. IB-4 cells were found to adhere to the tissue culture vessel through a component of the fetal bovine serum. By using blocking monoclonal antibodies to cell-surface molecules and serum proteins, IB-4 cells were found to use alpha V beta 3 integrin (CD51/CD61) and serum VN as the adhesive molecules. alpha V beta 3 integrin also mediated adhesion of IB-4 cells to human serum VN and to purified VN and FN. This constitutive adherence was not enhanced by phorbol ester treatment and was inhibited by RGD-containing peptides, in contrast to the homotypic adhesion of NAD-20 cells, which was mediated by beta 2 integrin CD11a/CD18 and its ligand ICAM-1 (CD54). Since VN is a component of both lymphoid tissue matrix and plasma, adhesion to this protein may affect functions and activities of B lymphocytes.

Topics: Amino Acid Sequence; Animals; Antibodies, Monoclonal; B-Lymphocytes; Blood Proteins; Cattle; CD11 Antigens; CD18 Antigens; Cell Adhesion; Cell Adhesion Molecules; Cell Line, Transformed; Edetic Acid; Fetal Blood; Flow Cytometry; Fluorescent Antibody Technique; Glycoproteins; Humans; Integrins; Intercellular Adhesion Molecule-1; Molecular Sequence Data; Oligopeptides; Receptors, Cytoadhesin; Receptors, Vitronectin; Tetradecanoylphorbol Acetate; Vitronectin

We show that the mechanism of fibronectin fibril formation on the blastocoel roof of the Xenopus embryo is comparable to that in other systems. Fibril assembly is inhibited by RGD peptide, by an amino-terminal fragment of fibronectin, and by cytochalasin B. When added exogenously, intact fibronectin, but not a 110 kDa cell binding fragment of fibronectin, is incorporated into fibrils. Thus, the blastocoel roof of Xenopus represents a valid model system for the study of fibronectin fibril formation in situ. Moreover, we show that fibril formation can be induced experimentally in this system. Examination of fibril elongation by double-labelling experiments reveals that individual, unbranched fibronectin fibrils grow only at one end, i.e. in a unipolar fashion. The rate of elongation is 4.7 microns/min. Most fibrils grow only for a short time, and the increase in total fibril length per cell is driven by the repeated initiation of new fibrils. Assembly of fibronectin into fibrils precedes cross-linking of fibronectin into multimers in this system.

Topics: Animals; Blastocyst; Cytochalasin B; Embryo, Nonmammalian; Fibronectins; Oligopeptides; Urea; Xenopus laevis

Ligands that bind mammalian cell surface integrins with high affinity can mediate cellular internalization. We show that particles of the bacteriophage fd that display the cyclic integrin-binding peptide sequence GGCRGDMFGC in a proportion of their major coat protein subunits bind to cells and are efficiently internalized. In the displayed peptide the conformation of the RGD motif is restricted within a hairpin loop formed by a disulfide bridge between the 2 cysteine residues. Cellular internalization of phage was demonstrated by confocal and non-confocal immunofluorescence microscopy of tissue-cultured cells incubated with phage particles. The phage were contained in juxtanuclear vesicles in the same serial sections as transferrin receptor but were not colocalized with the cell surface marker alkaline phosphatase. Cell binding and internalization was inhibited by preincubation of cells with the integrin-binding peptide GRGDSP, whereas the control peptide GRGESP had no inhibitory effect. These results indicate that cyclic integrin-binding peptides can be used to target and enter cells and that it should be possible to exploit such peptides for the introduction of DNA, drugs, or other macromolecules.

Topics: Amino Acid Sequence; Base Sequence; Capsid; Capsid Proteins; Cell Adhesion; Cell Line; Humans; Inovirus; Integrins; Microscopy, Fluorescence; Molecular Sequence Data; Oligodeoxyribonucleotides; Oligopeptides; Peptides, Cyclic; Recombinant Fusion Proteins

Interactions between cells from human giant cell tumors of bone and the extracellular matrix protein laminin were studied. Cells were capable of recognizing this substratum via a RGD-independent mechanism. Recognition induces adhesion and spreading onto laminin. This protein triggered the release of cellular FN which in turn enhanced recruitment of the beta 1 chain-containing integrin receptor.

Topics: Amino Acid Sequence; Bone Neoplasms; Cell Adhesion; Fibronectins; Giant Cell Tumor of Bone; Humans; Integrin beta1; Integrins; Laminin; Molecular Sequence Data; Oligopeptides; Osteoclasts; Receptors, Laminin; Tumor Cells, Cultured

We have investigated the heat- and autoclave-resistant properties of the cell-spreading activity of vitronectin, a cell-spreading glycoprotein in animal blood plasma. Vitronectin heated at 100 degrees C for 10 min or autoclaved at 121 degrees C at 1.2 kg/cm2 for 20 min retained the same cell-spreading activity as native vitronectin. In contrast, fibronectin and type-I collagen treated in the same way lost their activity almost completely. GRGDSP remarkably inhibited the cell-spreading activity of native, heated and autoclaved vitronectins. GRGESP did not inhibit the activity of native vitronectin, but, unexpectedly, partially inhibited the activity of both heated and autoclaved vitronectins. In SDS-polyacrylamide gel analysis under reducing conditions, vitronectin heated at 100 degrees C migrated mainly as a monomer, but autoclaved vitronectin migrated at both the top and front of the gel instead of at the position of the monomer. The change in molecular size during the heat- and autoclave treatments was partially prevented by adding 10 mM dithiothreitol or 2% 2-mercaptoethanol to the protein solution.

Topics: Amino Acid Sequence; Animals; Cell Movement; Collagen; Dithiothreitol; Electrophoresis, Polyacrylamide Gel; Fibronectins; Glycoproteins; Hot Temperature; Mercaptoethanol; Molecular Sequence Data; Oligopeptides; Vitronectin

Integrin alpha IIb beta 3 (platelet GPIIb-IIIa) binds fibrinogen via recognition sequences such as Arg-Gly-Asp (RGD). Fibrinogen binding requires agonist activation of platelets, whereas the binding of short synthetic RGD peptides does not. We now find that RGD peptide binding leads to changes in alpha IIb beta 3 that are associated with acquisition of high affinity fibrinogen-binding function (activation) and subsequent platelet aggregation. The structural specificities for peptide activation and for inhibition of ligand binding are similar, indicating that both are consequences of occupancy of the same site(s) on alpha IIb beta 3. Thus, the RGD sequence is a trigger of high affinity ligand binding to alpha IIb beta 3, and certain RGD-mimetics are partial agonists as well as competitive antagonists of integrin function.

Topics: Amino Acid Sequence; Blood Platelets; Fibrinogen; Humans; Integrins; Molecular Sequence Data; Oligopeptides; Platelet Membrane Glycoproteins

The Arg-Gly-Asp tripeptide (RGD) plays a widespread role in cell-to-cell and cell-to-matrix recognition. We demonstrated that an RGD-containing peptide (Arg-Gly-Asp-Val, RGDV) inhibits both oolemmal binding and penetration of zona-free hamster eggs by human spermatozoa in vitro when added to the incubation medium. These results suggest that RGD-containing proteins may play a role in sperm-oolemmal interactions required for fertilization.

Topics: Animals; Cell Adhesion; Cricetinae; Female; Male; Oligopeptides; Ovum; Sperm-Ovum Interactions; Spermatozoa