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L Catanzariti

Publications and source records attributed to L Catanzariti.

17 recordsLinked to original sources
PubMed1994

Activation of cAMP-dependent protein kinase alters the chromatin structure of the urokinase-type plasminogen activator gene promoter.

In LLC-PK1 cells, the urokinase-type plasminogen activator (uPA) gene is induced by two of the major signal transduction pathways, the protein kinase C (PKC) and the cAMP-dependent protein kinase (PKA) pathways. We have analyzed the chromatin structure of 26 kb of the uPA gene locus and have shown that PKA activation but not PKC activation induce major chromatin structural alterations in the uPA gene promoter. In uninduced cells, several DNase I hypersensitive (HS) sites were detected in the 5' and 3' flanking regions but not in the transcribed region. Two of the sites correspond to previously characterized regulatory sites: a cAMP responsive site at nucleotide position -3500 with respect to the initiation site, and the PEA3/AP1 site at -2100 that mediates PKC activation. After the activation of PKA but not PKC, a strong HS site was induced at -2600. Functional analysis of this region revealed cAMP responsive activity. Chromatin structural alterations again brought about specifically by PKA but not by PKC were were also detected in the upstream of the promoter by topoisomerase I cleavage site analysis, with two prominent sites appearing at -2800 and -3300. These results suggest that the strong cAMP induction of the uPA gene requires structural alterations that permit cooperative interactions between the multiple cAMP responsive sites.

Animals↗
PubMed1994

A novel mobile element inserted in the alpha spectrin gene: spectrin dayton. A truncated alpha spectrin associated with hereditary elliptocytosis.

Nonviral retrotransposons, retropseudogenes, and short interspersed nuclear elements (SINEs) are mobile DNA segments capable of transposition to new genomic locations, where they may alter gene expression. De novo integration into specific genes has been described in both germ and somatic cells. We report a family with hereditary elliptocytosis and pyropoikilocytosis associated with a truncated alpha-spectrin protein. We present the biochemical characteristics of this abnormal protein and show that the alpha-spectrin gene is disrupted by a mobile element resulting in exon skipping. This element causes duplication of the insertion site and is terminated by a long poly-A tail downstream of multiple consensus polyadenylation signals. Southern blot analysis of human genomic DNA, using this element as probe, reveals one to three copies per individual. This element has no homology to any previously reported sequence and therefore appears to be a member of a novel family of mobile elements.

Base Sequence↗
PubMed1993

A novel expression system for Gs-coupled receptors.

Renal epithelial cells LLC-PK1 secrete high amounts of urokinase-type plasminogen activator (uPA) when stimulated through the cAMP-signaling pathway. Here we show that this characteristic can be used to identify rapidly LLC-PK1-derived cell lines expressing heterologous receptors that couple to Gs-proteins. A genomic clone encoding the mouse beta 2 adrenergic receptor (beta 2AR) was transfected stably into LLC-PK1 cells. Drug-resistant colonies were subsequently stimulated with isoproterenol and screened for the secretion uPA activity. Positive clones displayed dose-dependent uPA activity in response to isoproterenol, specifically bound the beta 2AR-agonist iodocyanopindolol and expressed beta 2AR-mRNA. The functional coupling of beta 2AR expression to the inducible uPA gene establishes that LLC-PK1 cells can be used to assay for beta 2AR (and beta 2AR-agonist) function. Our data suggest that this system can be used for functional expression of other heterologous receptors that couple to Gs-proteins.

Animals↗
PubMed1992

A recombinant calcitonin receptor independently stimulates 3',5'-cyclic adenosine monophosphate and Ca2+/inositol phosphate signaling pathways.

Calcitonin (CT), a polypeptide hormone, regulates calcium homeostasis by activating surface receptors coupled to stimulation of adenylyl cyclase in bone and kidney cells. CT has also been reported to increase cytoplasmic Ca2+ in osteoclasts and renal tubule cells. Signaling pathways activated by a recombinant porcine renal calcitonin receptor transiently expressed in HEK-293 cells were studied. In cells expressing the recombinant CT receptor, salmon CT stimulated cAMP accumulation (EC50, 0.16 nM) and synthesis of inositol phosphates (IP; EC50, 3.7 nM). Two other recombinant receptors, the m1-muscarinic acetylcholine receptor and the LH receptor, activated synthesis of either IP or cAMP, respectively, but not both. Stable expression of the CT receptor in a CT receptor-deficient cell line, M18, restored the cells' ability to increase cytoplasmic Ca2+ in response to salmon CT. These results show that a single recombinant CT receptor can independently activate effector pathways mediated by cAMP and IP/Ca2+.

Animals↗