Pregnanes that bind to the digitalis receptor

Steroid binding domains of Na,K-ATPase and the nuclear hormone receptors share amino acid sequence homologies. In a ouabain radioligand assay, the potencies of series of planar or bent steroid moieties suggest that the domain in Na,K-ATPase can accommodate compounds with a planar configuration. The A/B -cis, C/D-cis steroid configuration in the cardenolides, in conjunction with appropriate substituents at the 3 and 17 positions, may represent a fortuitous "fit" for the exogenous compounds. It remains to be determined if the putative physiological digitalis-like substance is a member of a hormonal steroid family, an endogenous ouabain-like compound or both.     

Internet use and ties that bind.

Replies to comments by T. Silverman (see record 1999-11125-007), J. Rierdan (see record 1999-11125-008), and J. S. Shapiro (see record 1999-11125-009) regarding the original article by Kraut et al (see record 1998-10886-001) on the impact of Internet usage on social relations and depression. The authors respond to the concerns of the previous authors. In response to Silverman, they note that most online relationships formed by participants in their study resulted primarily in informational rather than emotional support, unlike the participants in Silverman's group. In response to Rierdan, the authors argue that the importance of results was not in the size of the effects, but in their direction; even small negative changes experienced by many people using the Internet can be significant. The authors also respond to Shapiro's methodological concerns and her alternative explanation of results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oligonucleotide inhibitors of human thrombin that bind distinct epitopes

Thrombin, a multifunctional serine protease, recognizes multiple macromolecular substrates and plays a key role in both procoagulant and anticoagulant functions. The substrate specificity of thrombin involves two electropositive surfaces, the fibrinogen-recognition and heparin-binding exosites. The SELEX process is a powerful combinatorial methodology for identifying high-affinity oligonucleotide ligands to any desired target. The SELEX process has been used to isolate single-stranded DNA ligands to human thrombin. Here, a 29-nucleotide single-stranded DNA ligand to human thrombin, designated 60-18[29], with a Kd of approximately 0.5 nM is described. DNA 60-18[29] inhibits thrombin-catalyzed fibrin clot formation in vitro. Previously described DNA ligands bind the fibrinogen-recognition exosite, while competition and photocrosslinking experiments indicate that the DNA ligand 60-18[29] binds the heparin-binding exosite. DNA 60-18[29] is a quadruplex/duplex with a 15-nucleotide "core" sequence that has striking similarity to previously described DNA ligands to thrombin, but binds with 20 to 50-fold higher affinity. The 15-nucleotide core sequence has eight highly conserved guanine residues and forms a G-quadruplex structure. A single nucleotide within the G-quadruplex structure can direct the DNA to a distinct epitope. Additional sequence information in the duplex regions of ligand 60-18[29] contribute to greater stability and affinity of binding to thrombin. A low-resolution model for the interaction of DNA 60-18[29] to human thrombin has been proposed.     

DNA ligands that bind tightly and selectively to cellobiose

Cell surface oligosaccharides have been shown to play essential biological roles in such diverse biological phenomena as cellular adhesion, molecular recognition, and inflammatory response. The development of high-affinity ligands capable of selectively recognizing a variety of small motifs in different oligosaccharides would be of significant interest as experimental and diagnostic tools. As a step toward this goal we have developed DNA ligands that recognize the disaccharide cellobiose, whether in soluble form or as the repeating unit of the polymer, cellulose. These DNA "aptamers" bind with high selectivity to cellobiose with little or no affinity for the related disaccharides lactose, maltose, and gentiobiose. Thus, the DNA ligands can discriminate sugar epimers, anomers, and disaccharide linkages.     

In vitro selection of aptamers that bind to ribosome-inactivating toxins

Ribosome-inactivating proteins, such as ricin, pepocin and gypsophilin, catalyze the hydrolysis of a single N-glycosidic bond at a specific position in rRNAs. Aptamers targeting pepocin were selected from a random sequence RNA pool that spanned 30 positions. After 8 rounds, the anti-pepocin aptamers were sequenced and a conserved hairpin motif was identified. Interestingly, the selected motif is quite different from the toxin-binding domains of rRNAs.     

Grandparents' visitation rights: Legalizing the ties that bind.

In recent years, statutes granting grandparents legal standing to petition for legally enforcable visitation with their grandchildren—even over parental objection—have been passed in all 50 states. This psycholegal review critically examines the origins of and justifications for this important change in family law, some of the psychological assumptions underlying this policy (e.g., the role of grandparents in child development), problems in judicial determinations of whether visitation is in a child's best interest, and both intended and unintended consequences for family functioning arising from this policy. In the end, although efforts to ensure multigenerational supports for children are admirable in the abstract, there are some significant risks in using legal policies for achieving this goal. Directions for further contributions from social scientists, as well as future directions in the evolution of grandparent visitation policy, are outlined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural consensus in ligand-protein docking identifies recognition peptide motifs that bind streptavidin

ALD affects a large segment of the population in the United States, both old and young, and men and women of all races and ethnicities. Many chronic diseases inevitably advance to a stage that results in significant respiratory impairment and disability. Although the causes of some of the diseases are known and the diseases may be preventable, the overall absolute burden of illness in the population is rising because of an enlarging population and newer therapeutic approaches. This is evident despite the lack of consistent and comparable data estimates for all diseases from national database resources. Where the data exist, it is evident that the cost related to the morbidity and mortality of these illnesses is substantial and consumes a significant proportion of health care expenditures. Both morbidity and mortality estimates, as well as cost estimates, are conservative and are likely underestimates of the true overall impact of ALD on the US economy.     

Identification of cellular proteins that bind the central conserved region of p53

The bacterial fusion protein between glutathione S-transferase and the central conserved region of human p53(GST-p53) was purified and fixed on the beads and then used in the binding assay with radiolabeled cell extract from human hepatocarcinoma cell line, Hep3B. The binding assay disclosed the presence of cellular proteins that interact with GST-p53 but not with GST. SV40 large T antigen abrogated the bindings of two cellular proteins with molecular weights of 50 kda and 40 kda. The binding of the proteins to p53 was observed in a cell cycle-dependent manner. These two proteins are candidate cellular proteins which regulate the function of p53.     

Biomimetic peptides that engage specific integrin-dependent signaling pathways and bind to calcium phosphate surfaces

Many important matrix proteins involved in bone remodeling contain separate domains that orient the protein on hydroxyapatite and interact with target cell receptors, respectively. We have designed two synthetic peptides that mimic the dual activities of these large, complex proteins by binding to calcium phosphate minerals and by engaging integrin-dependent signaling pathways in osteoblasts. The addition of either PGRGDS from osteopontin or PDGEA from collagen type I to the HAP-binding domain of statherin (N15 domain) did not alter its alpha-helical structure or diminish its affinity for hydroxyapatite. Immobilized N15-PGRGDS bound MC3T3-E1 osteoblasts predominantly via the alpha v beta 3 integrin and induced focal adhesion kinase (FAK) phosphorylation at comparable levels to immobilized osteopontin. Immobilized N15-PDGEA bound MC3T3-E1 osteoblasts predominantly through the alpha 2 beta 1 integrin and induced similar levels of FAK phosphorylation. Although both peptides induced FAK phosphorylation with similar time courses, only the N15-PDGEA peptide induced ERK1/2 phosphorylation, showing that these peptides are also capable of engaging integrin-specific signaling pathways. This peptide system can be used to study adhesion-dependent control of signaling in the context of the relevant biomineral surface and may also be useful in biomaterial and tissue engineering applications.     

Characterization of peptides that bind the tumor-associated Thomsen-Friedenreich antigen selected from bacteriophage display libraries

Peptides with high affinities and specificities for numerous proteins and nucleic acids have been previously identified from random peptide bacteriophage display libraries. Here, random peptide bacteriophage display libraries were used to identify sequences that bound the cancer-associated Thomsen-Friedenreich glycoantigen (T antigen). The T antigen, present on most malignant cells, contains an immunodominant Gal beta1 --> 3GalNAc alpha disaccharide unmasked on the surfaces of most carcinomas. This antigen has been postulated to be involved in tumor cell aggregation and metastasis. Two 15 amino acid random peptide bacteriophage display libraries were affinity selected with glycoproteins displaying T antigen on their surfaces. Sequence analysis revealed that many of the peptides shared homology with sugar recognition sites in several carbohydrate-binding proteins. A comparison of affinity selected sequences from both libraries yielded a common motif (W-Y-A-W/F-S-P) rich in aromatic amino acids. Four peptides, corresponding to the affinity selected sequences, were chemically synthesized and characterized for their carbohydrate recognition properties. The synthetic peptides exhibited high specificities and affinities to T antigen displayed on asialofetuin or conjugated to bovine serum albumin (Kd = 5 nM for MAP-P30 binding to asialofetuin) as well as free T-antigen disaccharide in solution (Kd = 10 microM for MAP-P30, 20 microM for P10). Two peptides, P30 and P10, demonstrated high affinities and specificities for both asialofetuin and T antigen in solution. Iodination of a lone tyrosine residue in each sequence dramatically reduced their abilities to bind T antigen, suggesting that the tyrosine residue plays an important role in carbohydrate recognition. That these peptides are of functional significance is evidenced by the ability of both P30 and P10 to inhibit asialofetuin-mediated melanoma cell aggregation in vitro and to compete with peanut lectin for binding to T antigen displayed on the surface of MDA-MB-435 breast carcinoma cells in situ.     

Predicting peptides that bind to MHC molecules using supervised learning of hidden Markov models

Cells in the lateral hypothalamus and in the arcuate nucleus play prominent roles in the central control of food intake; however, a neurochemical link connecting these potential components of a hypothalamic circuitry regulating energy metabolism remains to be established. In the present study, the topographical relationship between cells expressing mRNAs encoding melanin-concentrating hormone and the newly discovered neuropeptide family hypocretins/orexins was studied in the rat and mouse lateral hypothalamus by using double-labeling in situ hybridization. Cells expressing the two mRNAs formed completely distinct populations, with hypocretin/orexin cells located primarily perifornically and in the magnocellular lateral hypothalamic nucleus; melanin-concentrating hormone cells extended in a wider area both laterally and periventricularly and appeared to partly surround the hypocretin/orexin population. In the arcuate nucleus, cells expressing neuropeptide Y and agouti gene-related protein were studied by routine fluorescence and/or confocal microscopy immunohistochemistry. Double staining demonstrated that a large proportion of the neuropeptide Y-positive cell bodies in this nucleus also contained agouti gene-related protein-like immunoreactivity. Moreover, these two peptides also coexisted in nerve terminals surrounding and in close relationship to perikarya and processes of both hypocretin/orexin- and melanin-concentrating hormone-immunoreactive cells in the lateral hypothalamus, whereby the former appeared to receive a more dense innervation. These results thus provide evidence for an arcuate-lateral hypothalamic neuropeptide Y/agouti gene-related protein pathway. Furthermore, the results implicate hypocretin/orexin and melanin-concentrating hormone-expressing cells as downstream targets in neuropeptide Y-induced feeding.     

The ties that bind what is known to the recognition of what is new.

Recognition success varies with how information is encoded (e.g., level of processing) and with what is already known as a result of past learning (e.g., word frequency). This article presents the results of experiments showing that preexisting connections involving the associates of studied words facilitate their recognition regardless of whether the words are intentionally encoded or are incidentally encoded under semantic or nonsemantic conditions. Words are more likely to be recognized when they have either more resonant connections coming back to them from their associates or more connections among their associates. Such results occur even though attention is never drawn to these associates. Regression analyses showed that these connections affect recognition independently of frequency, so the present results add to the literature showing that prior lexical knowledge contributes to episodic recognition. In addition, equations that use free-association data to derive composite strength indices of resonance and connectivity were evaluated. Implications for theories of recognition are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Novel members of the Vesl/Homer family of PDZ proteins that bind metabotropic glutamate receptors

Vesl-1S (186 amino acids, also called Homer) is a protein containing EVH1- and PDZ-like domains whose expression in the hippocampus is regulated during long term potentiation (LTP), one form of synaptic plasticity thought to underlie memory formation (Kato, A., Ozawa, F., Saitoh, Y., Hirai, K., and Inokuchi, K. (1997) FEBS Lett. 412, 183-189; Brakeman, P. R., Lanahan, A. A., O'Brien, R., Roche, K., Barnes, C. A., Huganir, R. L., and Worley, P. F. (1997) Nature 386, 284-288). Here we report additional members of the Vesl/Homer family of proteins, Vesl-1L and Vesl-2. Vesl-1L (366 amino acids), a splicing variant of Vesl-1S, shares N-terminal 175 amino acids with Vesl-1S and contains additional amino acids at the C terminus. Vesl-2 (354 amino acids) was highly related to Vesl-1L in that both contain EVH1- and PDZ-like domains at the N terminus (86% conservation) and an MCC (mutated in colorectal cancer)-like domain and a leucine zipper at the C terminus. In contrast to vesl-1S, we observed no changes in the levels of vesl-1L and vesl-2 mRNAs during dentate gyrus LTP. All these proteins interacted with metabotropic glutamate receptors (mGluR1 and mGluR5) as well as several hippocampal proteins in vitro. Vesl-1L and Vesl-2, but not Vesl-1S, interacted with each other through the C-terminal portion that was absent in Vesl-1S. Vesl-1L and Vesl-2 may mediate clustering of mGluRs at synaptic junctions. We propose that Vesl-1S may be involved in the structural changes that occur at metabotropic glutamatergic synapses during the maintenance phase of LTP by modulating the redistribution of synaptic components.     

Haemoglobin binding with haptoglobin. Unequivocal demonstration that the beta-chains of human haemoglobin bind to haptoglobin

Haptoglobin binding to haemoglobin and its isolated alpha- and beta-chains was studied by use of a highly sensitive solid-phase radiometric assay. As expected, adsorbents of haemoglobin bound 125I-labelled haptoglobin more efficiently than did adsorbents of the alpha-chain. However, unexpectedly, adsorbents of the beta-chain were found to be essentially identical with those of the alpha-chain in their ability to bind haptoglobin. These results demonstrate, unequivocally, the ability of beta-chains to bind to haptoglobin, and indicate that this assay is particularly convenient and useful for studying haptoglobin interactions with haemoglobin and its alpha- and beta-chains.