The all-D-configuration segment containing the IKVAV sequence of laminin A chain has similar activities to the all-L-peptide in vitro and in vivo

Using Chemistry To Recreate the Complexity of the Extracellular Matrix: Guidelines for Supramolecular Hydrogel-Cell Interactions

Hydrogels have emerged as a promising class of extracellular matrix (ECM)-mimicking materials in regenerative medicine. Here, we briefly describe current state-of-the-art of ECM-mimicking hydrogels, ranging from natural to hybrid to completely synthetic versions, giving the prelude to the importance of supramolecular interactions to make true ECM mimics. The potential of supramolecular interactions to create ECM mimics for cell culture is illustrated through a focus on two different supramolecular hydrogel systems, both developed in our laboratories. We use some recent, significant findings to present important design principles underlying the cell-material interaction. To achieve cell spreading, we propose that slow molecular dynamics (monomer exchange within fibers) is crucial to ensure the robust incorporation of cell adhesion ligands within supramolecular fibers. Slow bulk dynamics (stress-relaxation─fiber rearrangements, τ1/2 ≈ 1000 s) is required to achieve cell spreading in soft gels (<1 kPa), while gel stiffness overrules dynamics in stiffer gels. Importantly, this resonates with the findings of others which specialize in different material types: cell spreading is impaired in case substrate relaxation occurs faster than clutch binding and focal adhesion lifetime. We conclude with discussing considerations and limitations of the supramolecular approach as well as provide a forward thinking perspective to further understand supramolecular hydrogel-cell interactions. Future work may utilize the presented guidelines underlying cell-material interactions to not only arrive at the next generation of ECM-mimicking hydrogels but also advance other fields, such as bioelectronics, opening up new opportunities for innovative applications.

Macroporous hydrogels derived from aqueous dynamic phase separation

A method to generate injectable macroporous hydrogels based on partitioning of polyethylene glycol (PEG) and high viscous polysaccharides is presented. Step growth polymerization of PEG was used to initiate a phase separation and the formation of a connected macroporous network with tunable dimensions. The possibilities and physical properties of this new category of materials were examined, and then applied to address some challenges in neural engineering. First, non-degradable macroporous gels were shown to support rapid neurite extension from encapsulated dorsal root ganglia (DRGs) with unprecedented long-term stability. Then, dissociated primary rat cortical neurons could be encapsulated with >95% viability, and extended neurites at the fast rate of ≈100 μm/day and formed synapses, resulting in functional, highly viable and long-term stable 3D neural networks in the synthetic extracellular matrix (ECM). Adhesion cues were found unnecessary provided the gels have optimal physical properties. Normal electrophysiological properties were confirmed on 3D cultured mouse hippocampal neurons. Finally, the macroporous gels supported axonal growth in a rat sciatic nerve injury model when used as a conduit filling. The combination of injectability, tunable pore size, stability, connectivity, transparency, cytocompatibility and biocompatibility, makes this new class of materials attractive for a wide range of applications.

Laminin-111-derived peptides and cancer

Laminin-111 is a large trimeric basement membrane glycoprotein with many active sites. In particular, four peptides active in tumor malignancy studies have been identified in laminin-111 using a systematic peptide screening method followed by various assays. Two of the peptides (IKVAV and AG73) are found on the α1 chain, one (YIGSR) of the β1 chain and one (C16) on the γ1 chain. The four peptides have distinct activities and receptors. Since three of the peptides (IKVAV, AG73 and C16) strongly promote tumor growth, this may explain the potent effects laminin-111 has on malignant cells. The peptide, YIGSR, decreases tumor growth and experimental metastasis via a 32/67 kD receptor while IKVAV increases tumor growth, angiogenesis and protease activity via integrin receptors. AG73 increases tumor growth and metastases via syndecan receptors. C16 increases tumor growth and angiogenesis via integrins. Identification of such sites on laminin-111 will have use in defining strategies to develop therapeutics for cancer.

Structural requirement of fibrogenic laminin-derived peptide A119 (LSNIDYILIKAS) for amyloid-like fibril formation and cellular activity

A119 peptide (LSNIDYILIKAS), derived from the mouse laminin α1 chain sequence (residues 1321-1332), promotes cell attachment, neurite outgrowth, and amyloid-like fibril formation. In this study, we evaluated the structural requirements of A119 for biological activities and amyloid-like fibril formation. The attachment of the cell to A119 was inhibited by heparin, and using syndecan- and glypican-overexpressed cells, it was determined that A119 specifically binds to syndecans. We also evaluated the critical residues for A119 activities using a set of alanine-substituted peptides. Cell attachment activity was significantly reduced in the Leu(1)-, Ser(2)-, Asn(3)-, Ile(4)-, Ile(7)-, Ile(9)-, and Lys(10)-substituted alanine peptides. Residues Ile(4), Ile(7), Ile(9), and Lys(10) were important for neurite outgrowth activity. Congo red staining and electron microscopic examination revealed that the Ile(4), Ile(7), Ile(9), and Ser(12) residues of A119 were required for amyloid-like fibril formation. These data suggest that the Ile residues are critical for the amyloid-like fibril formation, cell attachment, and neurite outgrowth activity of A119. Furthermore, an enantiomer of A119 showed similar amyloid-like fibril formation and increased levels of cell attachment and FAK signal transduction. These findings shed light on the mechanism of amyloid-like fibril formation and demonstrate a relationship between the ability to form amyloid-like fibrils and cell behavior.

Modification of gelation kinetics in bioactive peptide amphiphiles

Peptide amphiphiles (PAs) previously designed in our laboratory are known to self-assemble into nanofibers that exhibit bioactivity both in vitro and in vivo. Self-assembly can be triggered by charge neutralization or salt-mediated screening of charged residues in their peptide sequences, and the resulting nanofibers can form macroscopic gels at concentrations as low as 0.5% by weight. Controlling the kinetics of gelation while retaining the bioactivity of nanofibers could be critical in tailoring these materials for specific clinical applications. We report here on a series of PAs with different rates of gelation resulting from changes in their peptide sequence without changing the bioactive segment. The pre-existence of hydrogen-bonded aggregates in the solution state of more hydrophobic PAs appears to accelerate gelation kinetics. Mutation of the peptide sequence to include more hydrophilic and bulky amino acids suppresses formation of these nuclei and effectively slows down gelation through self-assembly of the nanofiber network. The ability to modify gelation kinetics in self-assembling systems without disrupting bioactivity could be important for injectable therapies in regenerative medicine.

SIKVAV, a laminin alpha1-derived peptide, interacts with integrins and increases protease activity of a human salivary gland adenoid cystic carcinoma cell line through the ERK 1/2 signaling pathway

Adenoid cystic carcinoma is a frequently occurring malignant salivary gland neoplasm. We studied the induction of protease activity by the laminin-derived peptide, SIKVAV, in cells (CAC2) derived from this neoplasm. Laminin alpha1 and matrix metalloproteinases (MMPs) 2 and 9 were immunolocalized in adenoid cystic carcinoma cells in vivo and in vitro. CAC2 cells cultured on SIKVAV showed a dose-dependent increase of MMP9 as detected by zymography and colocalization of alpha3 and alpha6 integrins. Small interfering RNA (siRNA) knockdown of integrin expression in CAC2 cells resulted in decreased adhesion to the peptide. SIKVAV affinity chromatography and immunoblot analysis showed that alpha3, alpha6, and beta1 integrins were eluted from the SIKVAV column, which was confirmed by mass spectrometry and a solid-phase binding assay. Small interfering RNA experiments also showed that these integrins, through extracellular signal-regulated kinase (ERK) 1/2 signaling, regulate MMP secretion induced by SIKVAV in CAC2 cells. We propose that SIKVAV increases protease activity of a human salivary gland adenoid cystic carcinoma cell line through alpha3beta1 and alpha6beta1 integrins and the ERK 1/2 signaling pathway.

Identification of multiple amyloidogenic sequences in laminin-1

Amyloid fibril formation is associated with several pathologies, including Alzheimer's disease, Parkinson's disease, type II diabetes, and prion diseases. Recently, a relationship between basement membrane components and amyloid deposits has been reported. The basement membrane protein, laminin, may be involved in amyloid-related diseases, since laminin is present in amyloid plaques in Alzheimer's disease and binds to amyloid precursor protein. Recently, we showed that peptide A208 (AASIKVAVSADR), the IKVAV-containing peptide, formed amyloid-like fibrils. We previously identified 60 cell adhesive sequences in laminin-1 using a total of 673 12-mer synthetic peptides. Here, we screened for additional amyloidogenic sequences among 60 cell adhesive peptides derived from laminin-1. We first examined amyloid-like fibril formation by the 60 active peptides with Congo red, a histological dye binding to many amyloid-like proteins. Thirteen peptides were stained with Congo red. Four of the 13 peptides promoted cell attachment and neurite outgrowth like the IKVAV-containing peptide. The four peptides also showed amyloid-like fibril formation in both X-ray diffraction and electron microscopic analyses. The amyloidogenic peptides contain consensus amino acid components, including both basic and acidic amino acids and Ser and Ile residues. These results indicate that at least five laminin-derived peptides can form amyloid-like fibrils. We conclude that the laminin-derived amyloidogenic peptides have the potential to form amyloid-like fibrils in vivo, possibly when laminin-1 is degraded.

Pregnancy loss and endometriosis: pathogenic role of anti-laminin-1 autoantibodies

Laminin-1 is a major multifunctional glycoprotein that forms an integral part of the scaffolding network of basement membranes, and is the earliest synthesized component during embryogenesis. This protein (alpha1beta1gamma1) plays an important role in basement membrane assembly and epiblast differentiation during embryonic development. Anti-laminin-1 autoantibodies are known to cause infertility and recurrent spontaneous abortion in animals. Recently, we reported that the presence of IgG anti-laminin-1 antibodies (Abs) in the blood is significantly associated with recurrent first-trimester miscarriages and subsequent negative pregnancy outcomes. Interestingly, these antibodies are also strongly associated with infertility, especially infertility caused by endometriosis. Laminin-alpha1, laminin-beta1, and laminin-gamma1 mRNAs were also detected in 90% of endometriotic lesions, and all laminin-alpha1, laminin-beta1, and laminin-gamma1 chains were localized to the basement membranes of glandular epithelium in endometriotic peritoneal lesions. ELISA showed specific reactivity of the autoantibodies to a particular region of the laminin-1 molecule, that is, the alpha1 chain G domain. IgM monoclonal anti-laminin-1 Abs, which we recently established, also recognized the G domain and cross-reacted with human alpha1 chain located in the basement membrane of the glandular epithelium of human endometrium. We also established an animal model that produced high titers of anti-laminin-1 Abs after immunization with mouse laminin-1. Anti-laminin-1 Abs from the immunized mice caused a higher fetal resorption rate with lower embryonic and placental weights. Thus, anti-laminin-1 Abs may be important in the development of autoimmune-mediated reproductive failures, and the assessment of the such antibodies may provide a novel means for noninvasive diagnosis of endometriosis.

Active sites in the carboxyl-terminal region of the laminin alpha chain in Drosophila neuronal cell spreading

An established Drosophila neuronal cell line (BG2-c6) proved to be useful to analyze laminin-mediated cell spreading and signal transduction [Takagi et al. (2000) Biochem Biophys Res Commun 270:482-487]. Here, we report, in addition to the whole molecule, the truncated alpha chain of Drosophila laminin (containing the entire carboxyl-terminal globular domain) and two dodecapeptides corresponding to the cell-binding sites identified in the alpha1 chain of mouse laminin were also active to stimulate BG2-c6 cell spreading. Our previous study [Takagi et al. (1996) J Biol Chem 271:18074-18081] revealed that these recombinant protein and synthetic peptides promoted neurite outgrowth in the primary cell culture system prepared from Drosophila embryo. Therefore, the similar effects by these proteins and peptides suggest the presence of a common mechanism of laminin and neuronal cell interaction working in both primary and established cells. One of the two active peptides contains the sequence SIKVGV. Its murine counterpart carries the sequence SIKVAV by which the interaction of laminin and cells is mediated. Furthermore, laminin-dependent BG2-c6 cell spreading was inhibited by heparin. This observation suggests that cell surface glycoproteins participate in the interaction of laminin and BG2-c6 cells.

Multifunctional peptide fibrils for biomedical materials

The Ile-Lys-Val-Ala-Val (IKVAV) containing peptide, A208 (AASIKVAVSADR, mouse laminin alpha1 chain 2097-2108), was recently found to form amyloid-like fibrils. Fibril formation is critical for its biological activities, including promotion of cell adhesion and neurite outgrowth. In the present study, we designed multifunctional peptide fibrils using the A208 peptide and an Arg-Gly-Asp (RGD)-containing fibronectin active sequence for biomedical applications. The fibronectin active sequence GRGDS (FN) or a scrambled sequence RSGGD (SC) were conjugated to either A208 or to A208S (AASVVIAKSADR), a scrambled peptide of A208, with a glycine as a spacer. The FN-A208 and SC-A208 peptides formed a gel and were stained with Congo red similar to that of A208, but FN-A208S and SC-A208S did not form a gel. These results indicate that FN-A208 and SC-A208 form amyloid-like fibrils similar to A208. A208 and SC-A208 promoted cell attachment with filopodia formation, and this adhesion was inhibited by the IKVAV-containing peptide, but not by EDTA or a GRGDS peptide. FN-A208 promoted cell attachment with well-organized actin stress fibers, and this adhesion was partially inhibited by either EDTA, GRGDS, or IKVAV. These data suggest that A208 binds to only IKVAV receptor(s) while the FN-A208 interacts with both integrins and the IKVAV receptor(s). We conclude that multifunctional peptide fibrils can be designed by conjugation of active peptides on A208 and that this construct has potential to serve as a bioadhesive for tissue regeneration and engineering.

In vitro effects of SIKVAV retro and retro-enantio analogues on tumor metastatic events

The SIKVAV peptide, located on the long arm of the laminin alpha1 chain, promotes cell adhesion, invasion and migration of tumor and endothelial cells, resulting in tumor growth, angiogenesis and metastasis. In this paper, we report the synthesis of the SIKVAV peptide and its retro (reverse l-amino acid order) and retro-enantio (reverse d-amino acid order) analogues and their effect on three critical steps in the metastatic process: cell-extracellular matrix protein (ECM) adhesion, cell migration and homotypic cell adhesion, using B16F10 melanoma cells. Results show that all peptides compete with laminin-1 cell attachment, but only SIKVAV induces peptide-cell adhesion. Retro analogue, but not retro-enantio, inhibits cell adhesion to SIKVAV, indicating that retro peptide recognizes the SIKVAV receptors while retro-enantio does not. Retro-enantio peptide is able to inhibit cell migration, by contrast of the SIKVAV chemoattractant activity. All three peptides reduce the homotypic cell adhesion in a dose-dependent manner, but retro-enantio sequence is the most effective reaching a 35% inhibition of controls at the higher concentration. These findings suggest that that both analogues of SIKVAV peptide, especially retro-enantio, may be considered as potential antimetastatic agents.

Ile-Lys-Val-Ala-Val (IKVAV)-containing laminin alpha1 chain peptides form amyloid-like fibrils

The Ile-Lys-Val-Ala-Val (IKVAV) sequence derived from laminin-1 promotes cell adhesion, neurite outgrowth, and tumor growth and metastasis. Here, we examined amyloid formation of an IKVAV-containing peptide (LAM-L: AASIKVAVSADR, mouse laminin alpha1 chain 2097-2108). The LAM-L peptide was stained with Congo red and exhibited fibrils in electron microscopy with a characteristic cross-beta X-ray diffraction pattern. Further, infrared spectra of LAM-L suggested a beta-sheet structure. These results indicate that LAM-L forms amyloid-like fibrils. We also examined amyloid-like fibril formation of LAM-L analogs. The neurite outgrowth activity of the LAM-L analogs was closely related to their amyloid-like fibril formation.

Identification of neurite outgrowth promoting sites on the laminin alpha 3 chain G domain

Laminins are expressed in specific tissues and are involved in various biological activities including promoting cell adhesion, growth, migration, neurite outgrowth, and differentiation. The laminin alpha3 chain is mainly located in the skin and is also expressed in the floor plate of the developing neural tube. Previously, we showed that the human laminin alpha3 chain LG4 module binds to syndecan-2/4, a membrane-associated proteoglycan, and promotes human fibroblast adhesion. Here, we have evaluated the neurite outgrowth activity of the laminin alpha3 chain LG4 and LG5 modules. Three overlapping recombinant proteins, which contained LG4 and/or LG5 modules of the human laminin alpha3 chain, were prepared using a mammalian cell expression system. Two proteins, rec-alpha3LG4-5 and rec-alpha3LG4, promoted cell attachment and neurite outgrowth of rat pheochromocytoma PC12 cells, but rec-alpha3LG5 was inactive. Twenty-two peptides covering the entire LG4 module were synthesized and tested for cell attachment and neurite outgrowth activity to identify active sites of the LG4 module. A3G75 (KNSFMALYLSKG, alpha3 chain 1411-1422) and A3G83 (GNSTISIRAPVY, alpha3 chain 1476-1487) promoted PC12 cell attachment and neurite outgrowth. Additionally, A3G75 and A3G83 inhibited PC12 cell attachment to rec-alpha3LG4. These results suggest that the A3G75 and A3G83 sites are important for PC12 cell attachment and neurite outgrowth in the laminin alpha3 chain LG4 module. We also conjugated the A3G75 and A3G83 peptides on chitosan membranes to test their potential as bio-materials. These peptide-conjugated chitosan membranes were more active for neurite outgrowth than the peptide-coated plates. These results suggest that the A3G75- and A3G83-conjugated chitosan membranes are applicable as bio-medical materials for neural tissue repair and engineering.

Laminin gamma 1 chain peptide, C-16 (KAFDITYVRLKF), promotes migration, MMP-9 secretion, and pulmonary metastasis of B16-F10 mouse melanoma cells

Laminin-1, a heterotrimer of alpha 1, beta 1, and gamma 1 chains specific to basement membrane, promotes cell adhesion and migration, proteinase secretion and metastases of tumour cells. Several active sites on the alpha 1 chain have been found to promote B16-F10 melanoma lung colonisation and here we have determined whether additional tumour promoting sites exist on the beta 1 and gamma 1 chains. Recently, we have identified novel cell adhesive peptides derived from laminin beta 1 and gamma 1 chains by systematic screening of synthetic peptides. Nine beta 1 peptides and seven gamma 1 peptides active for cell adhesion were tested for their effects on experimental pulmonary metastases of B16-F10 mouse melanoma cells in vivo. The most active adhesive peptide derived from the gamma 1 chain globular domain, C-16 (KAFDITYVRLKF), significantly enhanced pulmonary metastases of B16-F10 cells, whereas no other peptides showed enhancement. C-16 also stimulated migration of B16-F10 cells in the Boyden chamber assay in vitro. Furthermore, C-16 significantly induced the production of MMP-9 from B16-F10 cells. These results suggest that this specific laminin gamma 1 chain peptide has a metastasis-promoting activity and might be a new molecular target of anti-cancer treatment.

Identification of metastasis-promoting sequences in the mouse laminin alpha 1 chain

Laminin-1, a major basement membrane matrix glycoprotein, enhances adhesion, migration, and metastasis of tumor cells. We have screened 208 overlapping synthetic peptides covering the short and long arms of mouse laminin alpha1 chain for their adhesion activity with B16-F10 mouse melanoma cells. Cell adhesion activity was determined using various amounts of peptides coated on plastic dishes and by measuring cell adhesion on peptide-conjugated Sepharose beads. Nineteen peptides showed B16-F10 cell adhesion activity. Three peptides, designated A-13, -24, and -208, showed the strongest attachment activity in the plate assay, whereas 4 peptides, A-13, -51, -99, and -112, demonstrated the strongest cell adhesion when conjugated to beads. The 19 peptides were tested in vivo for their effect on experimental pulmonary metastasis by B16-F10 cells. Four peptides, A-13, -51, -64, and -119, significantly enhanced metastasis, with A-13 showing the strongest dramatic enhancement. The four metastasis-promoting peptides also stimulated migration of B16-F10 cells in the Boyden chamber assay in vitro with A-13 being the most potent stimulator. In addition, the 4 peptides inhibited laminin-induced cell attachment and migration, which indicates that these four sequences are possible functional B16-F10 cell binding sites in laminin-1. All the four sequences are located on the globular domains of the short arm. Other peptides, including strong adhesion-active peptides, A-24, -99, -112, and a scrambled A-13 peptide, did not stimulate either migration or metastasis. Thus, laminin-1 has multiple active sites in the globular domains of the short arm which promote migration and metastasis of B16-F10 cells.

Cell binding sequences in mouse laminin alpha1 chain

Laminin-1, a multifunctional glycoprotein of the basement membrane, consists of three different subunits, alpha1, beta1, and gamma1 chains. Previously, we used synthetic peptides to screen for biologically active sequences in the laminin alpha1 chain C-terminal globular domain (G domain) and identified several cell binding sequences (Nomizu, M., Kim, W. H., Yamamura, K., Utani, A., Song, S. Y., Otaka, A., Roller, P. P., Kleinman, H. K., and Yamada, Y. (1995) J. Biol. Chem. 270, 20583-20590). Here, we identify new cell binding sequences on the remainder of the laminin alpha1 chain by systematic peptide screening, using 208 overlapping synthetic peptides encompassing the central and N-terminal portions of the alpha1 chain. HT-1080 cell attachment activity to the peptides was evaluated using peptide-coated plastic substrates and peptide-conjugated Sepharose beads. Twenty five peptides showed cell attachment activities on either the peptide-coated plastic substrates and/or the peptide-conjugated Sepharose beads. A-13 (RQVFQVAYIIIKA) showed strongest cell attachment activity in both the assays. Cell attachment to 14 of the peptides was inhibited by heparin. EDTA and integrin antibodies inhibited cell adhesion to two of the peptides, A-13 and A-25, suggesting that these sites likely bind to integrins. These peptides inhibited cell attachment to laminin-1 but not to collagen I, suggesting these active sites are available on the intact molecule. Most of active sequences were localized on globular domains suggesting that these structures play a critical role in binding to cell-surface receptors.

Laminin alpha1 chain G domain peptide, RKRLQVQLSIRT, inhibits epithelial branching morphogenesis of cultured embryonic mouse submandibular gland

Active sequences from the laminin alpha1 and alpha2 chain carboxyl-terminal globular domains (G domain) have been identified by screening overlapping synthetic peptides in a number of biological assays (Nomizu et al. [1995] J. Biol. Chem. 270:20583-20590; Nomizu et al. [1996] FEBS Lett. 396:37-42). We have tested the activity of these peptides in submandibular gland explants of embryonic day 13 mice to determine the functional sites involved in organ development. The laminin alpha1 chain peptide, RKRLQVQLSIRT (residues 2719-2730 and designated AG-73), significantly inhibited epithelial branching morphogenesis. In contrast, other cell adhesive laminin alpha1 chain peptides including the AASIKVAVSADR and NRWHSIYITRFG failed to inhibit the branching. MG-73, a homologue of AG-73 from the laminin alpha2 chain, did not inhibit the branching. The alpha2 chain peptide had no effect, which may be due to the low levels of this laminin chain in day 13 mice. Laminin alpha2 chain-specific monoclonal antibodies strongly reacted with the basement membranes of developed acini but only weakly stained embryonic day 13 submandibular epithelium. The expression of E-cadherin and alpha6 integrin, as detected by immunofluorescence, were unchanged in both AG-73 and control scramble peptide-treated epithelial cells of the explants. In contrast, immunostaining of nidogen/entactin showed that explants treated with AG-73 for 3 days had a discontinuous basement membrane. Explants treated for 3 days with control peptide showed a normal basement membrane. These results suggest that the region containing the AG-73 sequence of the laminin alpha1 chain is crucial for development of submandibular gland at early embryonic stages. The discontinuous basement membrane in AG-73-treated explants may indicate an important role for this region in basement membrane assembly.

Identification of cell binding sequences in mouse laminin gamma1 chain by systematic peptide screening

Laminin-1, a major component of basement membranes, consists of three different chains designated alpha1, beta1, and gamma1 and has diverse biological functions. We have identified cell binding sites on the mouse laminin gamma1 chain, using systematic screening of 165 overlapping synthetic peptides covering the entire chain. We identified 12 cell binding sequences using HT-1080 human fibrosarcoma and B16-F10 mouse melanoma cells in two independent assays employing peptide-conjugated Sepharose beads and peptide-coated dishes. Four peptides (C-16, C-28, C-64, and C-68) located on the globular domains of the gamma1 chain were the most active and showed dose-dependent cell attachment. Cell attachment to C-68 was inhibited by EDTA and by anti-alpha2beta1 integrin antibodies. Cell attachment to C-16 and C-64 was partially inhibited by EDTA but was not inhibited by anti-integrin antibodies. EDTA and anti-integrin antibodies did not affect cell attachment to C-28. The four peptides were tested in adhesion and differentiation assays with endothelial, neuronal, and human salivary gland cells. C-16 was the most active for all of the cells, whereas the other three peptides showed cell type specificity in their activities. The active core sequences of C-16, C-28, C-64, and C-68 are YVRL, IRVTLN, TTVKYIFR, and SIKIRGTY, respectively. These sequences are highly conserved among the different species and in the laminin gamma2 chain. These results suggest that the specific sequences on the laminin gamma1 chain are biologically active and interact with distinct cell surface receptors.

An all-D amino acid peptide model of alpha1(IV)531-543 from type IV collagen binds the alpha3beta1 integrin and mediates tumor cell adhesion, spreading, and motility

Type IV collagen promotes integrin-mediated cell adhesion, spreading, and motility. Several regions within the triple-helical domain of type IV collagen have been identified as tumor cellular recognition sites. Among these regions, the alpha1(IV)531-543 sequence, designated L-Hep-III, promotes integrin-mediated tumor cell adhesion and directly binds to the alpha3beta1 integrin [Miles, A. J., et al. (1994) J. Biol. Chem. 269, 30939-30945; Miles, A. J., et al. (1995) J. Biol. Chem. 270, 29047-29050]. We have presently compared the activities of the all-d enantiomeric peptide model of alpha1(IV)531-543, designated D-Hep-III, with L-Hep-III, for promoting the adhesion, spreading, and motility of metastatic melanoma and breast carcinoma cells. D-Hep-III was found to support melanoma and breast carcinoma cell adhesion, spreading, and motility in a dose-dependent fashion similar to that of L-Hep-III. The adhesions of melanoma and breast carcinoma cells to both type IV collagen and fibronectin were effectively inhibited by L-Hep-III and D-Hep-III. Melanoma cell invasion of the basement membrane was also inhibited by D-Hep-III. Characterization of the cell surface receptor for D-Hep-III was acheived via cell adhesion assays and affinity chromatography using monoclonal antibodies against integrin subunits. Immunoprecipitation analysis following EDTA elution from a D-Hep-III affinity column indicated that D-Hep-III binds to the alpha3beta1 integrin but not to the alpha2 or alpha6 integrin subunits. In summary, these studies demonstrate that an all-D model of the alpha1(IV)531-543 sequence mimics the biological activities of the all-L peptide. D-Hep-III is the first all-D peptide that has been shown to promote tumor cell adhesion, spreading, and migration, inhibit tumor cell adhesion and migration on type IV collagen and invasion of the basement membrane, and bind directly to an integrin. Due to the resistance to proteolysis, all-D receptor-binding peptides such as D-Hep-III have great potential for in vivo studies and as therapeutic agents.

Band 3 Peptides Block the Adherence of Sickle Cells to Endothelial Cells In Vitro

Malaria-parasitized erythrocytes have increased endothelial adherence due to exposure of previously buried intramembranous sites of band 3. Because sickle erythrocytes also show increased adhesiveness and because the membrane portion of band 3 is aggregated in both types of cells, we examined the role of band 3 in sickle cell adhesiveness. Synthetic peptides derived from the second and third exofacial, interhelical regions of band 3 completely inhibited the abnormal adherence of sickle cells to an endothelial monolayer in a static assay. This effect was observed independently of plasma factors, required micromolar levels of peptide, was sequence-specific, and was found with both L- and D-isomers. The active peptides also inhibited the increased adherence induced by low-dose calcium loading of normal red blood cells. Finally, a monoclonal antibody against an active peptide specifically immunostained a fraction of sickle cells. These findings implicate a role for band 3 in at least one type of sickle cell adhesiveness via the exposure of normally cryptic membrane sites.

Antiproliferative and antitumor activities of D-reverse peptides derived from the second type-1 repeat of thrombospondin-1

The extracellular matrix glycoprotein thrombospondin-1 (TSP1) inhibits angiogenesis, endothelial cell growth, motility and adhesion. Peptides from the type I repeats of TSP1 mimic the adhesive and growth inhibitory activities of the intact protein and specifically interact with heparin and transforming growth factor-beta (TGF beta). To define the structural basis for the antiangiogenic activities of these peptides, we prepared analogs of the TSP1 peptide KRFKQDGGWSHWSPWSSC. L-forward, L-reverse, and D-reverse (retro-inverso) analogs displayed identical activities for binding to heparin, demonstrating a lack of stereospecificity for heparin binding. The L-reverse and D-reverse peptides, however, had somewhat decreased abilities to activate latent TGF beta. Conjugation of the forward peptides through a C-terminal thioether and the reverse peptides through an N-terminal thioether to polysucrose abolished the adhesive activity of the peptides and enhanced their antiproliferative activities for endothelial and breast carcinoma cells stimulated by fibroblast growth factor-2. Their antiproliferative activities were independent of latent TGF beta activation, because substitution of an Ala residue for the essential Phe residue in the TSP1 type-1 repeat peptide increased their potency for inhibiting TSP1 binding to heparin and for inhibiting endothelial cell proliferation. Although the conjugated peptides were inactive in vivo, an unconjugated retro-inverso analog of the native TSP peptide inhibited breast tumor growth in a mouse xenograft model. Thus, these TSP-derived peptide analogs antagonize endothelial growth through their heparin-binding activity rather than through activation of latent TGF beta or increasing cell adhesion. These stable analogs may therefore be useful as therapeutic inhibitors of angiogenesis stimulated by fibroblast growth factor-2.

All-D-enantiomers of beta-amyloid exhibit similar biological properties to all-L-beta-amyloids

The amyloidogenic peptide beta-amyloid has previously been shown to bind to neurons in the form of fibrillar clusters on the cell surface, which induces neurodegeneration and activates a program of cell death characteristic of apoptosis. To further investigate the mechanism of Abeta neurotoxicity, we synthesized the all-D- and all-L-stereoisomers of the neurotoxic truncated form of Abeta (Abeta25-35) and the full-length peptide (Abeta1-42) and compared their physical and biological properties. We report that the purified peptides exhibit nearly identical structural and assembly characteristics as assessed by high performance liquid chromatography, electron microscopy, circular dichroism, and sedimentation analysis. In addition, both enantiomers induce similar levels of toxicity in cultured hippocampal neurons. These data suggest that the neurotoxic actions of Abeta result not from stereoisomer-specific ligand-receptor interactions but rather from Abeta cellular interactions in which fibril features of the amyloidogenic peptide are a critical feature. The promiscuous nature of these beta-sheet-containing fibrils suggests that the accumulation of amyloidogenic peptides in vivo as extracellular deposits represents a site of bioactive peptides with the ability to provide inappropriate signals to cells leading to cellular degeneration and disease.

Peptide inhibition of glomerular deposition of an anti-DNA antibody

Antibodies to double-stranded DNA are pathognomonic of systemic lupus erythematosus and deposit in the kidneys of lupus patients to cause glomerulonephritis. Recent data suggest that a significant proportion of anti-DNA antibodies may cross-react with renal antigens and be sequestered in the kidney by virtue of this cross-reactivity. If this is true, antigenic competition for pathogenic antibodies might prevent their deposition in kidneys and the ensuing tissue damage. To generate surrogate antigens that could be used for this purpose, we have used peptide display phage libraries to identify peptides that react with R4A, a pathogenic mouse monoclonal anti-DNA antibody that deposits in glomeruli. We have demonstrated that the peptides bind in or near the double-stranded DNA binding site. Furthermore, the peptides are bound preferentially by the R4A antibody as compared with two closely related antibodies derived from it, one of which deposits in renal tubules and one of which displays no renal pathogenicity. Administration of one of these peptides in a soluble form protects mice from renal deposition of the R4A anti-DNA antibody in vivo. This represents a new therapeutic approach in systemic lupus erythematosus that focuses on protecting target organs from antibody mediated injury.

Aspartate residue 7 in amyloid beta-protein is critical for classical complement pathway activation: implications for Alzheimer's disease pathogenesis

Fibrillar amyloid beta-protein has been implicated in the pathogenesis of Alzheimer's disease because of its neurotoxicity and its ability to activate complement. Reactive microglia, astrocytes and complement (C') components (reviewed in ref. 6) are associated with senile plaques, the fibrillar, beta-sheet assemblies of amyloid beta-peptide found predominantly in brain from individuals with AD (ref. 7). These indications of inflammatory events are not prevalent in the nonfibrillar "diffuse" plaques often seen in age-matched control cases without dementia. Clinical studies over the past several years have correlated the use of anti-inflammatory drugs with a decrease in the incidence and progression of AD dementia and/or dysfunction, supporting a role for gliosis and inflammation in AD pathogenesis (reviewed in ref. 6). C5a, a product of C' activation, is chemotactic for microglia. Thus, complement activation provides a specific mechanism for recruiting reactive glial cells to the site of the fibrillar amyloid beta-protein plaque, which could lead to inflammatory events, neuronal dysfunction and degeneration. With the use of truncated amyloid beta-peptides, the region of amyloid beta-protein limited by residues 4 and 11 has been identified as critical in the interaction between amyloid beta-protein and C1q, the recognition component of the classical complement pathway (CCP), which results in the activation of C'. Furthermore, substitution of an isoaspartic acid for aspartic acid at amyloid beta-protein residue 7 resulted in the complete elimination of CCP-activating activity. A molecular model of this interaction has been generated that should be useful in the design of candidate therapeutic inhibitors of CCP activation by amyloid beta-protein.

Active peptides from the carboxyl-terminal globular domain of laminin alpha2 and Drosophila alpha chains

The laminin alpha1 chain carboxyl-terminal globular domain (G domain) contains multiple biological activities. Recently, we identified five cell binding sequences from the G domain by screening with overlapping 12-mer peptides encompassing the entire domain. The structures of these five sequences in the alpha1 chain are conserved in the corresponding regions of the different laminin alpha chains. Here we characterize the adhesion activities of the corresponding peptide segments from both the mouse laminin alpha2 chain and Drosophila laminin alpha chain using peptide-coated plastic plates and peptide-conjugated Sepharose beads. Using several cell lines, the laminin alpha2 chain peptides showed cell attachment and/or spreading activities with cell type specificities. Cell spreading on MG-10 was inhibited by integrin antibodies. Four of the Drosophila laminin peptides showed cell attachment activities. These results suggest that biologically active regions in the G domain are conserved in the laminin alpha1 and alpha2 chains, and that these regions in laminin play an important role in cell surface receptor interactions.

Conserved neuron promoting activity in Drosophila and vertebrate laminin alpha1

Drosophila S2 cells were transfected with constructs that code for two portions of the Drosophila laminin alpha chain. Construct recalphaL coded for domains III, I/II, and G of laminin alpha. Construct recalphaS coded for only the COOH-most 12% of the I/II domain and the G domain. The corresponding polypeptides were isolated and characterized from the culture media. The recalphaL chain partly formed disulfide-linked heterotrimers with the endogenously produced beta and gamma laminin chains. Like normal Drosophila laminin, a substrate coating of either recalphaL or recalphaS supported neuron differentiation and neurite extension of primary Drosophila embryo cell cultures. However, at the same low concentrations, only Drosophila laminin-1, but neither recalphaL nor recalphaS supported myogenesis in these cultures. Previously, an overlapping set of dodecapeptides that covered a region of the murine laminin alpha1 chain similar to recalphaS had been synthesized and tested for cell culture support properties (Nomizu, M., Kim, W. H., Yamamura, K., Utani, A., Otaka, A., Roller, P. P., Kleinman, H. K., and Yamada, Y. (1995) J. Biol. Chem. 270, 20583-20590). The Drosophila laminin alpha homologues of the six most active vertebrate dodecapeptides were now synthesized and tested as substrates for differentiation of primary Drosophila embryo cells. Peptides that contained either the Drosophila sequence SIKVGV or the murine homologue, SIKVAV, provided support for neurite extension.

Identification of cell binding sites in the laminin alpha 1 chain carboxyl-terminal globular domain by systematic screening of synthetic peptides

The laminin alpha 1 chain carboxyl-terminal globular domain has been identified as a site of multiple biological activities. Using a systematic screening for cell binding sites with 113 overlapping synthetic peptide beads that covered this domain, we found 19 potential active sequences. Corresponding synthetic peptides were evaluated for direct cell attachment, spreading, and inhibition of cell spreading to a laminin-1 substrate using several cell lines. Five peptides (AG-10, AG-22, AG-32, AG-56, and AG-73) showed cell attachment activities with cell-type specificities. Cell spreading on AG-10 was inhibited by beta 1 and alpha 6 integrin antibodies and on AG-32 was inhibited by beta 1, alpha 2, and alpha 6 integrin antibodies. In contrast, cell adhesion and spreading on peptide AG-73 were not inhibited by these antibodies. The minimum active sequences of AG-10, AG-32, and AG-73 were determined to be SIYITRF, IAFQRN, and LQVQLSIR, respectively. These sequences are highly conserved among the different species and different laminin alpha chains, suggesting that they play a critical role for biological function and for interaction with cell surface receptors.

Structure-activity study of a laminin alpha 1 chain active peptide segment Ile-Lys-Val-Ala-Val (IKVAV)

The IKVAV sequence, one of the most potent active sites of laminin-1, has been shown to promote cell adhesion, neurite outgrowth, and tumor growth. Here we have determined the structural requirements of the IKVAV sequence for cell attachment and neurite outgrowth using various 12-mer synthetic peptide analogs. All-L- and all-D-IKVAV peptides showed cell attachment and neurite outgrowth activities. In contrast, all-L- and all-D-reverse-sequence peptides were not active. Some of the analogs, in which the lysine and isoleucine residues of the IKVAV peptide were substituted with different amino acids, promoted cell attachment, but none of the analog peptides showed neurite outgrowth activity comparable to that of the IKVAV peptide. These results suggest that the lysine and isoleucine residues are critical for the biological functions of the IKVAV peptide.

Calmodulin interacts with amphiphilic peptides composed of all D-amino acids

Calmodulin binds to amphiphilic, helical peptides of a variety of amino-acid sequences. These peptides are usually positively charged, although there is spectroscopic evidence that at least one neutral peptide binds. The complex between calmodulin and one of its natural target peptides, the binding site for calmodulin on smooth muscle myosin light-chain kinase (RS20), has been investigated by crystallography and NMR which have characterized the interactions between the ligand and the protein. From these data, it appears that the calmodulin-binding surface is sterically malleable and van der Waals forces probably dominate the binding. To explore further this apparently permissive binding, we investigated the chiral selectivity of calmodulin using synthesized analogues of melittin and RS20 that consisted of only D-amino acids. Fluorescence and NMR measurements show that D-melittin and D-RS20 both bind avidly to calmodulin, probably in the same general binding site as that for peptides having all L-amino acids. The calmodulin-peptide binding surface is therefore remarkably tolerant sterically. Our results suggest a potentially useful approach to the design of non-hydrolysable or slowly hydrolysable intracellular inhibitors of calmodulin.

Biological distribution of 99mTc-labeled YIGSR and IKVAV laminin peptides in rodents: 99mTc-IKVAV peptide localizes to the lung

Two laminin-derived peptides containing either YIGSR or IKVAV (single amino acid code) sequences were radiolabeled with 99mTc and their biological distribution evaluated in rodents. Both 99mTc-peptides cleared rapidly from the circulation though the kidney, and to a lesser extent, through the liver. 99mTc-YIGSR peptide did not accumulate in any organ examined in normal, tumored, and emphysemic mice. The 99mTc-IKVAV peptide localized within 10 min to the lung of normal animals, resulting in lung-to-blood ratios of approximately 23:1. The 99mTc-IKVAV peptide localized to lung after submicron filtration and after intraperitoneal injection, suggesting that particulates do not major role in localization. Pre-incubation of 99mTc-IKVAV peptide in whole blood decreased lung localization, suggesting that margination of radiolabeled cells does not play a major role in the lung localization. When 99mTc-IKVAV was injected into mice with tumored lungs (melanoma), the lung uptake was markedly increased (up to 20% injected dose higher than control lungs) at all time points examined (10, 30, and 120 min). When 99mTc-IKVAV was injected into mice with genetic emphysema, the lung uptake was markedly decreased at all time points. The localization of the 99mTc-IKVAV-containing peptide to the lung is consistent with a receptor-based mechanism.

Functional domains of cell adhesion molecules

A number of molecules involved in cell adhesion (e.g. fibronectin, laminin, collagens I and IV, thrombospondin, entactin) have now been identified and the consequent roles that they play in the processes of growth, migration, differentiation and tumor spread have been described. Active sequences of the molecules have been identified using synthetic peptides derived from specific domains. Several adhesive molecules contain multiple active domains with different biological activities.