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A Lanahan

Publications and source records attributed to A Lanahan.

13 recordsLinked to original sources
PubMed1998

Identification of a Torpedo homolog of Sam68 that interacts with the synapse organizing protein rapsyn.

Nicotinic acetylcholine receptors (nAChRs) are initially expressed diffusely on the surface of myotubes and, in response to neuronally derived factors, cluster at the endplate to a final concentration of approximately 10000/microm2. The synaptic peripheral membrane protein rapsyn has been shown to mediate clustering of nAChRs in several systems. Here we describe the use of the yeast two-hybrid system to identify proteins that can interact with rapsyn. One of the clones we have identified is a Torpedo californica homolog of the Src-associated in mitosis protein (Sam68). We further show that Sam68, like rapsyn, is localized at the neuromuscular junction.

Amino Acid Sequence↗
PubMed1997

Selective alteration of long-term potentiation-induced transcriptional response in hippocampus of aged, memory-impaired rats.

Normal human aging is associated with selective changes in cognition that are attributable, in part, to dysfunction of hippocampal pathways. Rodents also exhibit age-dependent hippocampal dysfunction that results in spatial memory deficits and a correlated reduction in the maintenance of long-term potentiation (LTP). Although suprathreshold stimulus protocols result in normal LTP induction in aged rats, the ability to sustain this increase in synaptic efficacy is reduced in the old animals. The maintenance phase of LTP is known to be dependent on rapid, transcriptional events, and recent studies have identified signal transduction mechanisms that link glutamate-induced responses at the synapse with transcriptional responses at the nucleus. To examine the integrity of these signaling pathways in aged hippocampus, we monitored the induction of a panel of immediate early genes (IEGs) that are known to be transcriptionally activated after LTP-inducing stimuli, using a "reverse Northern" strategy. Here we report that a broad representation of IEGs are similarly induced in awake, behaving young adult and aged, memory-impaired rats. This indicates a general preservation of these presumptive signaling pathways during the aging process. Induced levels of c-fos mRNA, however, are significantly higher in the aged animals. These observations suggest that age-dependent hippocampal dysfunction may be associated with a selective change in the dynamic activity of signaling pathways upstream of c-fos, possibly involving calcium regulation.

Aging↗
PubMed1997

Huntingtin-associated protein 1 (HAP1) interacts with the p150Glued subunit of dynactin.

Huntington's disease (HD) is an inherited neurodegenerative disease caused by expansion of a polyglutamine repeat in the HD protein huntingtin. Huntingtin's localization within the cell includes an association with cytoskeletal elements and vesicles. We previously identified a protein (HAP1) which binds to huntingtin in a glutamine repeat length-dependent manner. We now report that HAP1 interacts with cytoskeletal proteins, namely the p150 Glued subunit of dynactin and the pericentriolar protein PCM-1. Structural predictions indicate that both HAP1 and the interacting proteins have a high probability of forming coiled coils. We examined the interaction of HAP1 with p150 Glued . Binding of HAP1 to p150 Glued (amino acids 879-1150) was confirmed in vitro by binding of p150 Glued to a HAP1-GST fusion protein immobilized on glutathione-Sepharose beads. Also, HAP1 co-immunoprecipitated with p150 Glued from brain extracts, indicating that the interaction occurs in vivo . Like HAP1, p150 Glued is highly expressed in neurons in brain and both proteins are enriched in a nerve terminal vesicle-rich fraction. Double label immunofluorescence experiments in NGF-treated PC12 cells using confocal microscopy revealed that HAP1 and p150 Glued partially co-localize. These results suggest that HAP1 might function as an adaptor protein using coiled coils to mediate interactions among cytoskeletal, vesicular and motor proteins. Thus, HAP1 and huntingtin may play a role in vesicle trafficking within the cell and disruption of this function could contribute to the neuronal dysfunction and death seen in HD.

Animals↗
PubMed1997

Huntingtin-associated protein 1 (HAP1) binds to a Trio-like polypeptide, with a rac1 guanine nucleotide exchange factor domain.

Huntington's disease (HD) occurs when the widely expressed protein huntingtin contains an expanded glutamine repeat. The selective degeneration and neuronal morphologic abnormalities of HD may involve interactions with proteins that bind to huntingtin, such as HAP1. The biological significance of this interaction is unclear because neither HAP1 nor huntingtin have significant homology to known proteins. Therefore, we sought to identify HAP1-binding proteins. Using the yeast two-hybrid system, we isolated a rat cDNA encoding part of a protein that interacts with HAP1, and we confirmed the specificity of this interaction using an in vitro protein-binding assay. We called the protein Duo because it is closely related to the human protein Trio but is shorter. Northern blot analysis indicates brain-specific expression of Duo. Human Duo contains a guanine nucleotide exchange factor (GEF) domain that is likely to be rac1-specific, a pleckstrin homology (PH) domain and spectrin-like repeat units. These data support the hypothesis that huntingtin is involved in vesicle trafficking and cytoskeletal functions, and raise the possibility of a role for huntingtin in the regulation of a ras-related signaling pathway.

Amino Acid Sequence↗
PubMed1995

A huntingtin-associated protein enriched in brain with implications for pathology.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by an expanding polyglutamine repeat in the IT15 or huntingtin gene. Although this gene is widely expressed and is required for normal development, the pathology of HD is restricted to the brain, for reasons that remain poorly understood. The huntingtin gene product is expressed at similar levels in patients and controls, and the genetics of the disorder suggest that the expansion of the polyglutamine repeat induces a toxic gain of function, perhaps through interactions with other cellular proteins. Here we report the identification of a protein (huntingtin-associated protein (HAP)-1) that binds to huntingtin. This binding is enhanced by an expanded polyglutamine repeat, the length of which is also known to correlate with the age of disease onset. The HAP-1 protein is enriched in the brain, suggesting a possible basis for the selective brain pathology of HD.

Amino Acid Sequence↗
PubMed1994

Cloning and characterization of a growth factor-inducible cyclooxygenase gene from rat intestinal epithelial cells.

Growth factors have been shown to play a role in intestinal epithelial growth regulation and transformation. Utilizing standard differential cloning techniques, we have isolated a growth factor-inducible gene (RS-2) from rat intestinal epithelial cells that has approximately 95% homology to the mouse mitogen-inducible cyclooxygenase (COX-2) at the amino acid level. This cDNA hybridizes to a approximately 4.5-kb mRNA from transforming growth factor (TGF)-alpha-stimulated rat intestinal epithelial (RIE-1) cells and is constitutively expressed in vivo in adult rat kidney and brain. Nuclear run-on experiments demonstrate that the increase of RS-2 mRNA after TGF-alpha stimulation is in part due to an increased transcription rate of the gene. The coding region for RS-2 was subcloned into a pCMV-2 expression vector, and the RS-2 protein was expressed in COS-1 cells. Microsomal fractions isolated from the COS-1 cells transfected with the RS-2 expression vector contained cyclooxygenase activity. In addition to the production of prostaglandins, the recombinant RS-2 protein also catalyzed the formation of three other eicosanoid products. In summary, we have cloned a mitogen-inducible cyclooxygenase gene from rat intestinal cells that is induced following growth factor stimulation.

Amino Acid Sequence↗
PubMed1992

Growth factor-induced delayed early response genes.

Growth factors induce the sequential expression of cellular genes whose products are thought to mediate long-term responses to the growth factors. In mouse 3T3 fibroblastic cells, the first genes to be expressed (immediate-early genes) are activated within minutes after the addition of platelet-derived growth factor, fibroblast growth factor, or serum. By cDNA cloning, we have identified genes that are activated after a delay of a few hours and several hours prior to serum-induced DNA replication. Activation of these delayed early response genes requires new protein synthesis, presumably the synthesis of immediate-early transcription factors described previously. Partial or complete sequencing of 13 different delayed early cDNAs, representing about 40% of the 650 primary cDNA isolates, revealed that 8 were related to known gene sequences and 5 were not. Among the former are cDNAs encoding nonhistone chromosomal proteins [HMGI(Y) and HMGI-C], adenine phosphoribosyltransferase (APRT), a protein related to human macrophage migration inhibitory factor (MIF), a protein of the major intrinsic protein (MIP) family homologous to the integral membrane protein of human erythrocytes, and cyclin CYL1. In 3T3 cells, the delayed early gene response to growth factors appears to be at least as complex as the immediate-early gene response previously described.

3T3 Cells↗
PubMed1989

jun-D: a third member of the jun gene family.

The protooncogene c-jun encodes a component of the transcription factor AP-1. Both murine c-jun and a related gene (jun-B) are rapidly activated in BALB/c3T3 cells by serum growth factors. We report here the cloning and analysis of a cDNA encoding a third member of the murine jun family, jun-D. The amino acid sequence encoded by jun-D has two extensive regions of homology with the other Jun proteins. One homology region includes the DNA-binding domain and sequences required for dimer formation and interaction with the Fos oncoprotein; the other includes the acidic sequence thought to be involved in gene activation. All three jun mRNAs are present in a variety of murine tissues and cell lines. In resting 3T3 cells, jun-D is expressed at a higher level compared to c-jun and jun-B, and its transcription is stimulated only slightly by serum growth factors. Thus, jun-D appears to be regulated differently than c-jun and jun-B.

Amino Acid Sequence↗
PubMed1989

A growth factor-responsive gene of murine BALB/c 3T3 cells encodes a protein homologous to human tissue factor.

Polypeptide growth factors rapidly induce the transcription of a set of genes that appear to mediate cell growth. We report that one of the genes induced in BALB/c mouse 3T3 cells encodes a transmembrane protein (mTF) homologous to human tissue factor, which is involved in the proteolytic activation of blood clotting. mTF mRNA is present in many murine tissues and cell lines. Our results raise the possibility that mTF may also play a role in cell growth.

Amino Acid Sequence↗
PubMed1986

Expression and structure of the human NGF receptor.

The nucleotide sequence for the human nerve growth factor (NGF) receptor has been determined. The 3.8 kb receptor mRNA encodes a 427 amino acid protein containing a 28 amino acid signal peptide, an extracellular domain containing four 40 amino acid repeats with six cysteine residues at conserved positions followed by a serine/threonine-rich region, a single transmembrane domain, and a 155 amino acid cytoplasmic domain. The sequence of the extracellular domain of the NGF receptor predicts a highly ordered structure containing a negatively charged region that may serve as the ligand-binding site. This domain is conserved through evolution. Transfection of a full-length cDNA in mouse fibroblasts results in stable expression of NGF receptors that are recognized by monoclonal antibodies to the human NGF receptor and that bind [125I]NGF.

Amino Acid Sequence↗
PubMed1986

The nerve growth factor receptor gene is at human chromosome region 17q12-17q22, distal to the chromosome 17 breakpoint in acute leukemias.

Genomic and cDNA clones for the human nerve growth factor receptor have been used in conjunction with somatic cell hybrid analysis and in situ hybridization to localize the nerve growth factor receptor locus to human chromosome region 17q12-q22. Additionally, part, if not all, of the nerve growth factor receptor locus is present on the translocated portion of 17q (17q21-qter) from a poorly differentiated acute leukemia in which the chromosome 17 breakpoint was indistinguishable cytogenetically from the 17 breakpoint observed in the t(15;17)(q22;q21) translocation associated with acute promyelocytic leukemia. Thus the nerve growth factor receptor locus may be closely distal to the acute promyelocytic leukemia-associated chromosome 17 breakpoint at 17q21.

Chromosome Mapping↗
PubMedDate not supplied

Immediate-early genes and synaptic function.

Classical studies have demonstrated a role for protein synthesis in long-term memory. The focus of our research is to identify the proteins that are essential for memory and to discover how they contribute to activity-dependent neuronal plasticity. We have developed whole-animal models that maximize the induction of activity-dependent genes and have used differential cloning techniques to identify a set of novel, neuronal immediate-early genes (IEGs). Neuronal IEGs encode transcription factors, cytoskeletal proteins, growth factors, metabolic enzymes, and proteins involved in signal transduction. The biochemical and cell biological properties of these molecules provide important insights into mechanisms that contribute to neuronal plasticity. Recently, we identified a subset of IEGs that appear to function at the synapse. These molecules extend the functional repertoire of IEGs and may provide insight into how IEGs can contribute to synapse-specific plasticity.

Animals↗