Biomedical subjects

Franco Ferracci

Publications and source records attributed to Franco Ferracci.

6 recordsLinked to original sources

PubMed2006

The neurological disorder associated with thyroid autoimmunity.

The neurological disorder associated with thyroid autoimmunity is an elusive disease that neurologists have learned to recognize in the last few years. The diagnosis is made, after excluding more common diseases, when neuropsychiatric symptoms develop in a patient with high serum concentrations of anti-thyroid antibodies. The clinical presentations of the disease and the many controversial issues surrounding the diagnosis, the pathogenesis, the role of thyroid autoantibodies, and the choice of therapy are reviewed and discussed in the light of the medical literature in English.

Autoantibodies↗

PubMed2006

Measurement of effector protein injection by type III and type IV secretion systems by using a 13-residue phosphorylatable glycogen synthase kinase tag.

Numerous bacterial pathogens use type III secretion systems (T3SSs) or T4SSs to inject or translocate virulence proteins into eukaryotic cells. Several different reporter systems have been developed to measure the translocation of these proteins. In this study, a peptide tag-based reporter system was developed and used to monitor the injection of T3S and T4S substrates. The glycogen synthase kinase (GSK) tag is a 13-residue phosphorylatable peptide tag derived from the human GSK-3beta kinase. Translocation of a GSK-tagged protein into a eukaryotic cell results in host cell protein kinase-dependent phosphorylation of the tag, which can be detected with phosphospecific GSK-3beta antibodies. A series of expression plasmids encoding Yop-GSK fusion proteins were constructed to evaluate the ability of the GSK tag to measure the injection of Yops by the Yersinia pestis T3SS. GSK-tagged YopE, YopH, LcrQ, YopK, YopN, and YopJ were efficiently phosphorylated when translocated into HeLa cells. Similarly, the injection of GSK-CagA by the Helicobacter pylori T4SS into different cell types was measured via phosphorylation of the GSK tag. The GSK tag provides a simple method to monitor the translocation of T3S and T4S substrates.

Amino Acid Sequence↗

PubMed2005

Selection and characterization of Yersinia pestis YopN mutants that constitutively block Yop secretion.

Secretion of Yop effector proteins by the Yersinia pestis plasmid pCD1-encoded type III secretion system (T3SS) is regulated in response to specific environmental signals. Yop secretion is activated by contact with a eukaryotic cell or by growth at 37 degrees C in the absence of calcium. The secreted YopN protein, the SycN/YscB chaperone and TyeA form a cytosolic YopN/SycN/YscB/TyeA complex that is required to prevent Yop secretion in the presence of calcium and prior to contact with a eukaryotic cell. The mechanism by which these proteins prevent secretion and the subcellular location where the block in secretion occurs are not known. To further investigate both the mechanism and location of the YopN-dependent block, we isolated and characterized several YopN mutants that constitutively block Yop secretion. All the identified amino-acid substitutions that resulted in a constitutive block in Yop secretion mapped to a central domain of YopN that is not directly involved in the interaction with the SycN/YscB chaperone or TyeA. The YopN mutants required an intact TyeA-binding domain and TyeA to block secretion, but did not require an N-terminal secretion signal, an intact chaperone-binding domain or the SycN/YscB chaperone. These results suggest that a C-terminal domain of YopN complexed with TyeA blocks Yop secretion from a cytosolic, not an extracellular, location. A hypothetical model for how the YopN/SycN/YscB/TyeA complex regulates Yop secretion is presented.

Amino Acid Substitution↗

PubMed2004

Hashimoto's encephalopathy: epidemiologic data and pathogenetic considerations.

BACKGROUND: Hashimoto's encephalopathy (HE) is a condition believed to complicate Hashimoto's thyroiditis (HT). The diagnosis is suspected in the presence of high levels of serum anti-thyroid antibodies. We have recently demonstrated that in patients with HE there is an intrathecal synthesis of anti-thyroid antibodies, and concluded that the diagnosis of HE should be based on this cerebrospinal fluid (CSF) finding. OBJECTIVE: getting an estimate of the prevalence of the disease, verifying the association with HT and investigating the pathogenetic role of anti-thyroid antibodies. METHODS: 34-months prospective study in a hospital setting serving a community of 150,000 people. Patients with unexplained symptoms of acute or subacute encephalopathy or myelopathy or with a history of thyroid disorders were selected for the measurement of anti-thyroid antibodies. In the presence of high serum levels of autoantibodies, the same tests were performed in the CSF. RESULTS: Twelve patients had increased concentrations of serum autoantibodies but HE was diagnosed only in nine patients. The estimated prevalence of HE is 2.1/100,000. Only six HE patients had also HT. Four patients received corticosteroids, five patients were not treated. Five patients improved, four patients spontaneously, one patient after corticosteroids. Repeated CSF examinations showed that the titer of CSF autoantibodies did not correlate with the clinical stage of the disease nor was influenced by corticosteroids. In addition, the course of symptoms was independent of therapy. CONCLUSIONS: The association of encephalopathy and high titers of anti-thyroid antibodies is not sufficient to make a diagnosis of HE. Independent of the clinical status of the thyroid gland, the intrathecal synthesis of autoantibodies is a distinctive marker of this elusive condition.

Adolescent↗

PubMed2004

Expression of a functional secreted YopN-TyeA hybrid protein in Yersinia pestis is the result of a +1 translational frameshift event.

YopN is a secreted protein that prior to secretion directly interacts with the cytosolic SycN/YscB chaperone complex and TyeA. This study identifies a secreted YopN-TyeA hybrid protein that is expressed by Yersinia pestis, but not by Yersinia enterocolitica. DNA sequence analysis and site-directed mutagenesis studies demonstrate that the hybrid protein is the result of a +1 translational frameshift event.

Amino Acid Sequence↗

PubMed2003

Translocation of YopE and YopN into eukaryotic cells by Yersinia pestis yopN, tyeA, sycN, yscB and lcrG deletion mutants measured using a phosphorylatable peptide tag and phosphospecific antibodies.

Yersinia pestis, the causative agent of plague, exports a set of virulence proteins called Yops upon contact with eukaryotic cells. A subset of these Yops is translocated directly into the cytosol of host cells. In this study, a novel protein tag-based reporter system is used to measure the translocation of Yops into cultured eukaryotic cells. The reporter system uses a small bipartite phosphorylatable peptide tag, termed the Elk tag. Translocation of an Elk-tagged protein into eukaryotic cells results in host cell protein kinase-dependent phosphorylation of the tag at a specific serine residue, which can subsequently be detected with phosphospecific antibodies. The YopN, TyeA, SycN, YscB and LcrG proteins function to prevent Yop secretion before host cell contact. The role of these proteins was investigated in the translocation of Elk-tagged YopE (YopE129-Elk) and YopN (YopN293-Elk) into HeLa cells. Y. pestis yopN, tyeA, sycN and yscB deletion mutants showed reduced levels of YopE129-Elk phosphorylation compared with the parent strain, indicating that these mutants translocate reduced amounts of YopE. We also demonstrate that YopN293-Elk is translocated into HeLa cells and that this process is more efficient in a Yersinia yop polymutant strain lacking the six translocated effector Yops. Y. pestis sycN and yscB mutants translocated reduced amounts of YopN293-Elk; however, tyeA and lcrG mutants translocated higher amounts of YopN293-Elk compared with the parent strain. These data suggest that TyeA and LcrG function to suppress the secretion of YopN before host cell contact, whereas SycN and YscB facilitate YopN secretion and subsequent translocation.

Antibodies↗