CLN3 loss disturbs membrane microdomain properties and protein transport in brain endothelial cells

Juvenile neuronal ceroid lipofuscinosis (JNCL) is a fatal childhood-onset neurodegenerative disorder caused by mutations in ceroid lipofuscinosis neuronal-3 (CLN3), a hydrophobic transmembrane protein of unresolved function. Previous studies indicate blood–brain barrier (BBB) defects in JNCL, and our earlier report showed prominent Cln3 expression in mouse brain endothelium. Here we find that CLN3 is necessary for normal trafficking of the microdomain-associated proteins caveolin-1, syntaxin-6, and multidrug resistance protein 1 (MDR1) in brain endothelial cells. Correspondingly, CLN3-null cells have reduced caveolae, and impaired caveolae- and MDR1-related functions including endocytosis, drug efflux, and cell volume regulation. We also detected an abnormal blood–brain barrier response to osmotic stress in vivo. Evaluation of the plasma membrane with fluorescent sphingolipid probes suggests

Adenoviral Gene Transfer Restores Lysyl Hydroxylase Activity in Type VI Ehlers-Danlos Syndrome

Type VI Ehlers-Danlos syndrome is a disease characterized by disturbed lysine hydroxylation of collagen. The disease is caused by mutations in lysyl hydroxylase 1 gene and it affects several organs including the cardiovascular system, the joint and musculoskeletal system, and the skin. The skin of type VI Ehlers-Danlos syndrome patients is hyperelastic, scars easily, and heals slowly and poorly. We hypothesized that providing functional lysyl hydroxylase 1 gene to the fibroblasts in and around wounds in these patients would improve healing. In this study we tested the feasibility of transfer of the lysyl hydroxylase 1 gene into fibroblasts derived from rats and a type VI Ehlers-Danlos syndrome patient (in vitro) and into rat skin (in vivo). We first cloned human lysyl hydroxylase 1 cDNA into a recombinant adenoviral vector (Ad5RSV-LH). Transfection of human type VI Ehlers-Danlos syndrome fibroblasts (about 20% of normal lysyl hydroxylase 1 activity) with the vector increased lysyl hydroxylase 1 activity in these cells to near or greater levels than that of wild type, unaffected fibroblasts. The adenoviral vector successfully transfected rat fibroblasts producing both β-galactosidase and lysyl hydroxylase 1 gene activity. We next expanded our studies to a rodent model. Intradermal injections of the vector to the abdominal skin of rats produced lysyl hydroxylase 1 mRNA and elevated lysyl hydroxylase 1 activity, in vivo. These data suggest the feasibility of gene replacement therapy to modify skin wound healing in type VI Ehlers-Danlos syndrome patients

Inhibition of Interleukin-1-Induced Effects in Synoviocytes Transduced with the Human IL-1 Receptor Antagonist cDNA Using an Adenoviral Vector

Overview summary Adenovirus-mediated gene transfer into the cells of the synovial membrane may provide a means to deliver therapeutically active proteins for the local modification of the immune response in inflammatory arthropathies. In this study, we infected type B human synoviocytes in vitro and rabbit synovial lining membrane in vivo with a recombinant human adenovirus containing the cDNA for the human interleukin-1 receptor antagonist protein (IL-1ra). Expression of human IL-1ra was observed both in the transduced synoviocytes in vitro and in the microenvironment of the transduced rabbit synovial membrane in vivo, and the functional activity of the transgenic IL-1ra was suggested by in vitro inhibition of interleukin-1 (IL-1)-induced prostaglandin E2 (PGE2) production and by in vivo inhibition of IL-1-induced glycosaminoglycan (GAG) degradation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63124/1/hum.1995.6.3-307.pd

Human hypoxanthine-guanine phosphoribosyltransferase: a single nucleotide substitution in cDNA clones isolated from a patient with Lesch-Nyhan syndrome (HPRTMidland)

We have determined the molecular basis for hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency in a patient J.H., with Lesch-Nyhan syndrome. Radioimmunoassay of lysates of erythrocytes or cultured B-lymphoblasts showed that this patient had no detectable HPRT enzyme activity or HPRT protein. HPRT-specific mRNA levels were normal by Northern analysis.We created a cDNA library from mRNA isolated from cultured lymphoblasts derived from this patient. Nucleotide sequencing of full-length HPRT cDNA clones revealed a single nucleotide (nt) substitution: a T-to-A transversion at nt 389. We have designated this variant HPRTMidland. The predicted amino acid (aa) substitution in HPRTMidland is a valine to aspartic acid at aa 130. This substitution is within 2 aa of the amino acid substitution in a previously defined HPRT variant, HPRTAnn Arbor. Both mutations are within a highly conserved sequence in the putative 5-phosphoribosyl-l-pyrophosphate-binding domain. The amino acid substitution in HPRTMidland causes a significant perturbation in the predicted secondary structure of this region. The HPRTMidland mutation affects a different domain of HPRT than the HPRTFlint mutation located at 167 nt away.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27178/1/0000176.pd

Pulmonary Inflammation Induced by Incomplete or Inactivated Adenoviral Particles

Overview summary The amount of pulmonary inflammation induced in mice by intratracheal administration of high doses of adenoviral vectors was compared to that induced by viral particles that lack the ability to express the genes that they contain. The number of inflammatory cells infiltrating the lung 6 days after particle administration was similar between animals receiving normal versus defective adenoviral particles.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63169/1/hum.1995.6.12-1553.pd

Genetic basis of hypoxanthine guanine phosphoribosyltransferase deficiency in a patient with the Lesch-Nyhan syndrome (HPRTFlint)

The molecular basis for complete hypoxanthine guanine phosphoribosyltransferase (HPRT) deficiency has been determined in a patient with Lesch-Nyhan syndrome. A B-lymphoblastoid cell line derived from this patient expresses normal amounts of HPRT mRNA yet no detectable immunoreactive protein as determined by radioimmunoassay. These findings suggest either a decreased rate of translation or accelerated degradation due to enhanced proteolytic susceptibility. cDNAs synthesized from this patient's RNA have a single nucleotide (nt) substitution, a C --> A transversion at nt 222. RNase A cleavage analysis confirms the presence of a mutation at this position within mRNA isolated from lymphoblasts from patient A.C. This transversion predicts a phenylalanine to leucine replacement at amino acid position 73 in the translated protein. We have designated this mutant HPRTFlint. The mutation in HPRTFlint disrupts a strongly conserved region among PRTases from Escherichia coli, rodents and man, suggesting an important role for this region for the normal function of HPRT. Since it is unlikely that this amino acid substitution alters the translational rate, we hypothesize that disruption of the secondary structure within this region renders HPRTFlint more susceptible to proteolysis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27367/1/0000393.pd

Connecdenn, a novel DENN domain-containing protein of neuronal clathrin-coated vesicles functioning in synaptic vesicle endocytosis

Clathrin-coated vesicles (CCVs) are responsible for the endocytosis of multiple cargo, including synaptic vesicle membranes. We now describe a new CCV protein, termed connecdenn, that contains an N-terminal DENN (differentially expressed in neoplastic versus normal cells) domain, a poorly characterized protein module found in multiple proteins of unrelated function and a C-terminal peptide motif domain harboring three distinct motifs for binding the α-ear of the clathrin adaptor protein 2 (AP-2). Connecdenn coimmunoprecipitates and partially colocalizes with AP-2, and nuclear magnetic resonance and peptide competition studies reveal that all three α-ear-binding motifs contribute to AP-2 interactions. In addition, connecdenn contains multiple Src homology 3 (SH3) domain-binding motifs and coimmunoprecipitates with the synaptic SH3 domain proteins intersectin and endophilin A1. Interestingly, connecdenn is enriched on neuronal CCVs and is present in the presynaptic compartment of neurons. Moreover, connecdenn has a uniquely stable association with CCV membranes because it resists extraction with Tris and high-salt buffers, unlike most other CCV proteins, but it is not detected on purified synaptic vesicles. Together, these observations suggest that connecdenn functions on the endocytic limb of the synaptic vesicle cycle. Accordingly, disruption of connecdenn interactions with its binding partners through overexpression of the C-terminal peptide motif domain or knock down of connecdenn through lentiviral delivery of small hairpin RNA both lead to defects in synaptic vesicle endocytosis in cultured hippocampal neurons. Thus, we identified connecdenn as a component of the endocytic machinery functioning in synaptic vesicle endocytosis, providing the first evidence of a role for a DENN domain-containing protein in endocytosis

Synthesis of normal and variant human hypoxanthine-guanine phosphoribosyltransferase in Escherichia coli

Naturally occurring mutations in hypoxanthine-guanine phosphoribosyltransferase (HPRT) have been identified by amino acid sequencing, cDNA cloning, and direct nucleotide sequencing of PCR-amplified transcripts. To determine the effect these mutations have on the catalytic properties of the molecule, knowledge of the three-dimensional structure of HPRT is required. A prerequisite for this, however, is the availability of a large amount of purified product for crystallization and x-ray diffraction analysis. For these reasons we have developed an effective means of producing high levels of human HPRT in Escherichia coli using the expression cassette PCR. By taking advantage of a T7 polymerase/promoter system, we have expressed both normal and variant human hprt sequences in E. coli. The proteins synthesized from these sequences are immunologically and enzymatically active, and are physically indistinguishable from the HPRT in B-lymphoblasts derived from normal and three HPRT-deficient subjects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31002/1/0000677.pd

Adenosine deamination in human transcripts generates novel microRNA binding sites

Animals regulate gene expression at multiple levels, contributing to the complexity of the proteome. Among these regulatory events are post-transcriptional gene silencing, mediated by small non-coding RNAs (e.g. microRNAs), and adenosine-to-inosine (A-to-I) editing, generated by adenosine deaminases that act on double-stranded RNA (ADAR). Recent data suggest that these regulatory processes are connected at a fundamental level. A-to-I editing can affect Drosha processing or directly alter the microRNA (miRNA) sequences responsible for mRNA targeting. Here, we analyzed the previously reported adenosine deaminations occurring in human cDNAs, and asked if there was a relationship between A-to-I editing events in the mRNA 3′ untranslated regions (UTRs) and mRNA:miRNA binding. We find significant correlations between A-to-I editing and changes in miRNA complementarities. In all, over 3000 of the 12 723 distinct adenosine deaminations assessed were found to form 7-mer complementarities (known as seed matches) to a subset of human miRNAs. In 200 of the ESTs, we also noted editing within a specific 13 nucleotide motif. Strikingly, deamination of this motif simultaneously creates seed matches to three (otherwise unrelated) miRNAs. Our results suggest the creation of miRNA regulatory sites as a novel function for ADAR activity. Consequently, many miRNA target sites may only be identifiable through examining expressed sequences