Search

A new case of Schnitzler's syndrome is reported in a 72-year old man hospitalized for severe deterioration of his general condition associated with recurrent ancient urticaria. Paraclinical examinations, which showed inflammatory syndrome, bone condensation and IgM monoclonal gammapathy, led to the diagnosis of Schnitzler's syndrome, first described in 1972. Twenty-two cases have now been published, characterized by vasculitic urticaria, osteosclerosis and IgM macroglobulinaemia. There is also severe inflammatory syndrome and the other immunological examinations are normal. Recent studies suggest the possibility of uncontrolled activity of interleukin-1 alpha. The condition is chronic and usually benign, but the fear of malignant transformation in the long term makes the therapeutic choice difficult.

Bacterial protein synthesis takes place in the cytoplasm, thus periplasmic and outer membrane proteins pass through the cytoplasmic membrane during their dispatch to the cell envelope. The exported proteins are synthesized as precursor that contains an extra amino-terminal sequence of amino-acids. This sequence, termed "signal sequence", is essential for transport of the envelope proteins through the inner membrane and is cleaved during the exportation process. Various hypotheses for the mechanism have been presented, and it is likely that no signal model will be suitable to the export of all cell envelope proteins. This review is focused on the relationship between the cytoplasmic membrane and the precursor form. The physiological state of the membrane - fluidity, membrane potential for instance - is the strategic requirement of exportation process. Precursors can be accumulated in whole cells with various treatments which alter the cytoplasmic membrane. This inhibition of processing is obtained by modification of unsaturated to saturated fatty acids ratio or with phenylethyl alcohol which perturbs the membrane fluidity, with uncoupler agents such as carbonyl cyanide m-chlorophenyl hydrazone which dissipate the proton motive force, or with hybrid proteins which get jamming in the membrane. However, little is known about the early steps of translocation process across the cytoplasmic membrane ; for instance, it is not clear yet whether energy is required for either or both of the first interaction membrane-precursor and the crossing through the membrane. Several studies have recently shown the presence of exportation sites and of proteins which might play a prominent role in the export process, but the mechanism of discrimination between outer membrane proteins and periplasmic proteins is unknown. Considerable work has been done by genetic or biochemical methods and we have now the first lights of the expert mechanism.