Biomedical subjects

Lori L Jennings

Publications and source records attributed to Lori L Jennings.

9 recordsLinked to original sources

PubMed2026

Large-Scale Proteomic Profiling of Incident Heart Failure and Its Subtypes in Older Adults.

BACKGROUND: Heart failure (HF) and its main subtypes, heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF), impose an enormous health burden on elders. Assessment of the circulating proteome to illuminate pathogenesis could open new opportunities for treatment. METHODS: We conducted a plasma proteomics screen of incident HF and its subtypes in 2 older population-based cohorts, the CHS (Cardiovascular Health Study) and the AGES-RS (Aging, Gene/Environment Susceptibility-Reykjavik Study). The 2 studies used SomaLogic platforms, with 4404 aptamers in common. Multivariable Cox models were fit to evaluate individual-protein associations with HF, HFpEF, and HFrEF separately in each cohort, and study-specific associations were combined by fixed-effects meta-analysis. Replication was performed in the ARIC (Atherosclerosis Risk in Communities) cohort. Two-sample Mendelian randomization of HF and its subtypes, along with colocalization analysis, was performed to support causal inference. RESULTS: Among 8599 participants, 1590 experienced incident HF (536 HFpEF, 471 HFrEF). There were 119 proteins associated with HF, 15 proteins with HFpEF, and 11 proteins with HFrEF, at Bonferroni-corrected significance. Among these, 9 have never previously been identified for cardiovascular diseases, and another 61 represent new associations with incident HF or its subtypes. Of these 70 proteins, 55 of the 66 available replicated externally. Mendelian randomization analysis revealed 7 proteins genetically associated with HF at nominal significance; 2 were separately associated with HFpEF, and another 2 with HFrEF. Seven of these 9 proteins (NPDC1 [neural proliferation differentiation and control protein 1], APOF [apolipoprotein F], LMAN2 [lectin, mannose-binding 2], ADIPOQ [adiponectin], CD14 [cluster of differentiation 14], ARHGAP1 [Rho GTPase-activating protein 1], C9 [complement 9]) showed new, possibly causal associations, although we did not detect evidence for colocalization. CONCLUSIONS: In this large-scale proteomic study involving 3 longitudinal cohorts of older adults, we identified and replicated 55 novel protein markers of HF or its subtypes, and 7 new, possibly causal proteins. These proteins may enhance risk prediction, improve understanding of pathobiology, and help prioritize targets for therapeutic development of these foremost disorders in elders.

Humans↗

PubMed2006

Gene selection, alternative splicing, and post-translational processing regulate neuroligin selectivity for beta-neurexins.

Neuroligins 1-4 are postsynaptic transmembrane proteins capable of initiating presynaptic maturation via interactions with beta-neurexin. Both neuroligins and beta-neurexins have alternatively spliced inserts in their extracellular domains. Using analytical ultracentrifugation, we determined that the extracellular domains of the neuroligins sediment as dimers, whereas the extracellular domains of the beta-neurexins appear monomeric. Sedimentation velocity experiments of titrated stoichiometry ratios of beta-neurexin and neuroligin suggested a 2:2 complex formation. The recognition properties of individual neuroligins toward beta-neurexin-1 (NX1beta), along with the influence of their splice inserts, were explored by surface plasmon resonance and affinity chromatography. Different neuroligins display a range of NX1beta affinities spanning more than 2 orders of magnitude. Whereas splice insert 4 in beta-neurexin appears to act only as a modulator of the neuroligin/beta-neurexin association, splice insert B in neuroligin-1 (NL1) is the key element regulating the NL1/NX1beta binding. Our data indicate that gene selection, mRNA splicing, and post-translational modifications combine to give rise to a controlled neuroligin recognition code with a rank ordering of affinities for particular neurexins that is conserved for the neuroligins across mammalian species.

Alternative Splicing↗

PubMed2005

A single mutation near the C-terminus in alpha/beta hydrolase fold protein family causes a defect in protein processing.

An Arg to Cys mutation in the extracellular domain of neuroligin-3 (NL3) was recently found in a twin set with autism [S. Jamain, H. Quach, C. Betancur, M. Rastam, C. Colineaux, I.C. Gillberg, H. Soderstrom, B. Giros, M. Leboyer, C. Gillberg, T. Bourgeron, Paris Autism Research International Sibpair Study, mutations of the X-linked genes encoding neuroligins NLGN3 and NLGN4 are associated with autism, Nat. Genet. 34 (2003) 27-29]. The Cys substitution in NL3 causes altered intracellular protein trafficking, intracellular retention and diminished association with its cognate partner, beta-neurexin [D. Comoletti, A. De Jaco, L.L. Jennings, R.E. Flynn, G. Gaietta, I. Tsigelny, M.H. Ellisman, P. Taylor, The R451C-neuroligin-3 mutation associated with autism reveals a defect in protein processing, J. Neurosci. 24 (2004) 4889-4893]. NL3, butyrylcholinesterase (BuChE), and acetylcholinesterase (AChE), as members of the (/(-hydrolase fold family of proteins, share over 30% of amino acid identity in their extracellular domains. In particular, Arg451 in NL3 is conserved in the alpha/beta-hydrolase fold family being homologous to Arg386 in BuChE and Arg395 in AChE. A Cys substitution at the homologous Arg in the BuChE was found studying post-succinylcholine apnea in an Australian population [T. Yen, B.N. Nightingale, J.C. Burns, D.R. Sullivan, P.M. Stewart, Butyrylcholinesterase (BCHE) genotyping for post-succinylcholine apnea in an Australian population, Clin. Chem. 49 (2003) 1297-308]. We have made the homologous mutation in the mouse AChE and BuChE genes and showed that the Arg to Cys mutations resulted in identical alterations in the cellular phenotype for the various members of the alpha/beta-hydrolase fold family proteins.

Hydrolases↗

PubMed2004

The Arg451Cys-neuroligin-3 mutation associated with autism reveals a defect in protein processing.

The neuroligins are a family of postsynaptic transmembrane proteins that associate with presynaptic partners, the beta-neurexins. Neurexins and neuroligins play a critical role in initiating formation and differentiation of synaptic junctions. A recent study reported that a mutation of neuroligin-3 (NL3), an X-linked gene, was found in siblings with autistic spectrum disorder in which two affected brothers had a point mutation that substituted a Cys for Arg451. To characterize the mutation at the biochemical level, we analyzed expression and activity of the mutated protein. Mass spectrometry comparison of the disulfide bonding pattern between the native and the mutated proteins indicates the absence of aberrant disulfide bonding, suggesting that the secondary structure of the mutated protein is conserved. However, the mutation separately affects protein expression and activity. The Cys mutation causes defective neuroligin trafficking, leading to retention of the protein in the endoplasmic reticulum. This, in turn, decreases the delivery of NL3 to the cell surface. Also, the small fraction of protein that reaches the cell membrane lacks or has markedly diminished beta-neurexin-1 (NX1beta) binding activity. Other substitutions for Arg451 allow for normal cellular expression but diminished affinity for NX1beta. Our findings reveal a cellular phenotype and loss of function for a congenital mutation associated with autistic spectrum disorders.

Amino Acid Substitution↗

PubMed2004

Structural characterization of recombinant soluble rat neuroligin 1: mapping of secondary structure and glycosylation by mass spectrometry.

Neuroligins (NLs) are a family of transmembrane proteins that function in synapse formation and/or remodeling by interacting with beta-neurexins (beta-NXs) to form heterophilic cell adhesions. The large N-terminal extracellular domain of NLs, required for beta-NX interactions, has sequence homology to the alpha/beta hydrolase fold superfamily of proteins. By peptide mapping and mass spectrometric analysis of a soluble recombinant form of NL1, several structural features of the extracellular domain have been established. Of the nine cysteine residues in NL1, eight are shown to form intramolecular disulfide bonds. Disulfide pairings of Cys 117 to Cys 153 and Cys 342 to Cys 353 are consistent with disulfide linkages that are conserved among the family of alpha/beta hydrolase proteins. The disulfide bond between Cys 172 and Cys 181 occurs within a region of the protein encoded by an alternatively spliced exon. The disulfide pairing of Cys 512 and Cys 546 in NL1 yields a structural motif unique to the NLs, since these residues are highly conserved. The potential N-glycosylation sequons in NL1 at Asn 109, Asn 303, Asn 343, and Asn 547 are shown occupied by carbohydrate. An additional consensus sequence for N-glycosylation at Asn 662 is likely occupied. Analysis of N-linked oligosaccharide content by mass matching paradigms reveals significant microheterogeneous populations of complex glycosyl moieties. In addition, O-linked glycosylation is observed in the predicted stalk region of NL1, prior to the transmembrane spanning domain. From predictions based on sequence homology of NL1 to acetylcholinesterase and the molecular features of NL1 established from mass spectrometric analysis, a novel topology model for NL three-dimensional structure has been constructed.

Amino Acid Sequence↗

PubMed2003

Characterization of the interaction of a recombinant soluble neuroligin-1 with neurexin-1beta.

Neuroligins, proteins of the alpha/beta-hydrolase fold family, are found as postsynaptic transmembrane proteins whose extracellular domain associates with presynaptic partners, proteins of the neurexin family. To characterize the molecular basis of neuroligin interaction with neurexin-beta, we expressed five soluble and exportable forms of neuroligin-1 from recombinant DNA sources, by truncating the protein before the transmembrane span near its carboxyl terminus. The extracellular domain of functional neuroligin-1 associates as a dimer when analyzed by sedimentation equilibrium. By surface plasmon resonance, we established that soluble neuroligins-1 bind neurexin-1beta, but the homologous alpha/beta-hydrolase fold protein, acetylcholinesterase, failed to associate with the neurexins. Neuroligin-1 has a unique N-linked glycosylation pattern in the neuroligin family, and glycosylation and its processing modify neuroligin activity. Incomplete processing of the protein and enzymatic removal of the oligosaccharides chain or the terminal sialic acids from neuroligin-1 enhance its activity, whereas deglycosylation of neurexin-1beta did not alter its association capacity. In particular, the N-linked glycosylation at position 303 appears to be a major determinant in modifying the association with neurexin-1beta. We show here that glycosylation processing of neuroligin, in addition to mRNA splicing and gene selection, contributes to the specificity of the neurexin-beta/neuroligin-1 association.

Acetylcholinesterase↗

PubMed2003

Direct analysis of the kinetic profiles of organophosphate-acetylcholinesterase adducts by MALDI-TOF mass spectrometry.

A sensitive matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry procedure has been established for the detection and quantitation of acetylcholinesterase (AChE) inhibition by organophosphate (OP) compounds. Tryptic digests of purified recombinant mouse AChE (mAChE) were fractionally inhibited by paraoxon to form diethyl phosphoryl enzyme. The tryptic peptide of mAChE that contains the active center serine residue resolves to a molecular mass of 4331.0 Da. Phosphorylation of the enzyme by paraoxon results in covalent modification of the active center serine and a corresponding increase in molecular mass of the tryptic peptide by 136 Da. The relative abundance of AChE peptides containing a modified active center serine strongly correlates with the fractional inhibition of the enzyme, achieving a detection range of phosphorylated to nonphosphorylated enzyme of 5-95%. Modifications of AChE by OP compounds resulting in dimethyl, diethyl, and diisopropyl phosphoryl adducts have been monitored with subpicomole amounts of enzyme. The individual phosphorylated adducts of AChE that result from loss of one alkyl group from the inhibited enzyme (the aging reaction) and the reappearance of unmodified AChE (spontaneous reactivation) have been resolved by the kinetic profiles and relative abundance of species. Further, the tryptic peptide containing the active center serine of AChE, isolated from mouse brain by anion-exchange and affinity chromatography, has been monitored by mass spectrometry. Native brain AChE, purified from mice treated with sublethal doses of metrifonate, has demonstrated that enzyme modifications resulting from OP exposure can be detected in a single mouse brain. For dimethyl phosphorylated AChE, OP exposure has been monitored by the ratio of tryptic peptide peaks that correspond to unmodified (uninhibited and/or reactivated), inhibited, and aged enzyme.

Acetylcholinesterase↗

PubMed2003

Differentiation between acetylcholinesterase and the organophosphate-inhibited form using antibodies and the correlation of antibody recognition with reactivation mechanism and rate.

Two types of polyclonal antibodies were generated from (a) a decapeptide sequence that includes the active site serine of acetylcholinesterase (anti-AChE10S) and (b) the identical decapeptide sequence phosphorylated at the active site serine of acetylcholinesterase (anti-AChE10SP). The anti-AChE10S antiserum was found to specifically recognize native, control, and vehicle-treated recombinant mouse AChE (rMoAChE) but did not recognize rMoAChE that was phosphorylated by the four organophosphate (OP) compounds tested. Conversely the anti-AChE10SP antiserum recognized phosphoserine rMoAChE that resulted from reaction with phosphorous oxychloride (POCl3) but did not recognize native or vehicle-treated rMoAChE. Anti-AChE10SP also did not recognize OP-AChE conjugates that resulted from the reaction of rMoAChE with other OP compounds that afford neutral or monoanionic phosphoserine groups thereby indicating a high specificity for a precise OP conjugate. Antisera recognition correlated well with the rates of enzyme inhibition, aging, and oxime-induced reactivation indicating these antisera can both quantify the extent and type of inhibition and also differentiate between select mechanisms of inhibition. The ability to discern mechanistic differences between native AChE and OP-AChE conjugates suggests that these antisera can be used to identify biomarkers of OP exposure in a mechanism-based approach.

Acetylcholinesterase↗

PubMed2002

Immunohistochemical variation of human equilibrative nucleoside transporter 1 protein in primary breast cancers.

Gemcitabine and capecitabine are nucleoside analogues used in chemotherapy strategies for the treatment of breast cancer. We previously demonstrated that deficiency in hENT1, the most abundant and widely distributed plasma membrane nucleoside transporter in human cells, confers high-level resistance to gemcitabine toxicity in vitro, whereas the relationship between hENT1 activity and capecitabine toxicity is unknown. To determine the relationship between capecitabine cytotoxicity and hENT1 abundance, cultured MDA-MB-435s human mammary carcinoma cells were exposed to graded concentrations of the capecitabine metabolites, 5'-deoxy-5-fluorouridine or 5-fluorouracil, in the presence and absence of nitrobenzylmercaptopurine ribonucleoside (NBMPR), a tight-binding inhibitor of hENT1. The presence of NBMPR reduced the cytotoxic effects of 5'-deoxy-5-fluorouridine, indicating that hENT1 also enabled cellular uptake of this capecitabine metabolite by breast cancer cells. We report here the development of an immunohistochemical method to assess the hENT1 abundance of malignant cells in solid tumors. Frozen sections of 33 primary breast cancers were stained with monoclonal antibodies raised against a synthetic peptide derived from the large intracellular loop of hENT1, and staining intensity was scored on a 0-4+ scale. hENT1 staining intensity varied markedly among breast samples (4 with score 0, 5 with score 1+, 7 with score 2+, 14 with score 3+, 3 with score 4+), suggesting that at least 9 of the tumors were hENT1 deficient. We conclude that because hENT1 deficiency has previously been associated with nucleoside drug resistance, immunohistochemical staining of hENT1 warrants further study as a predictive tool for guiding the appropriate use of gemcitabine and capecitabine in the treatment of breast cancer.

Affinity Labels↗