Activation of protein kinase C increases the extracellular release of the transmembrane amyloid protein precursor of Alzheimer's disease.

The beta A4 peptide is the major constituent of the amyloid core of abundant senile plaques found in the cerebral cortex of patients with Alzheimer's disease. This amyloid peptide is synthesized as part of a large transmembrane amyloid protein precursor or APP. In addition to the highly expressed transmembrane APP isoforms, an mRNA encoding a secreted APP lacking the transmembrane domain has been identified. A cleavage of the transmembrane protein also yields an extracellular soluble APP fragment. The effect of phorbol esters on the release of the extracellular APP was studied in transfected Chinese hamster ovary cells which stably express either a transmembrane or a secreted APP isoform. The activation of protein kinase C by phorbol-12,13-dibutyrate increased the extracellular release of the transmembrane APP resulting from its proteolytic cleavage, while 4-beta-phorbol, which does not activate protein kinase C, did not significantly affect the recovery of the soluble APP. On the contrary, the recovery of APP secreted in the culture medium without proteolytic cleavage was not increased by protein kinase C-mediated phosphorylation.

Simultaneous presence of different Borrelia burgdorferi genospecies in biological fluids of Lyme disease patients.

Oligonucleotide primers based on Borrelia burgdorferi sensu lato ospA gene sequences have been designed for use in the PCR to type all (SL primers) or each (GI to GIII primers) of the B. burgdorferi sensu lato genospecies involved in Lyme disease. These genospecies-specific primers were then used in the PCR on 24 biological fluids collected from 18 neuroborreliosis patients. Among the samples tested, 20 contained DNA from Borrelia garinii, 11 contained DNA from B. burgdorferi sensu stricto, and 10 contained DNA from Borrelia afzelii. In toto, 10 patients appeared to have been infected by a single genospecies and 8 were infected by more than one Lyme disease-associated genospecies. Serum specimens from six patients were absorbed with heterologous antigens and tested by Western blotting (immunoblotting). In four cases, residual immunodetection revealed specific epitopes of genospecies also detected by PCR; in two of them, the concordant results indicated pluri-infection of the patients. In the other two cases, Western blotting showed specific antibodies for two genospecies of Borrelia, while PCR detected DNA from only one. In summary, the data underscored the relatively high prevalence of pluri-infections in Lyme disease and confirmed the association of B. garinii with neuroborreliosis.