Biogenesis and exocytosis of enlargeosomes
Enlargeosomes were first discovered by patch camp electrophysiology by demonstrating the regulated exocytosis of small organelles in non-secretory cells, and by immunofluorescence, revealing that the distribution of their marker, Ahnak, does not coincide with that of the markers of other organelles. Subsequent data have revealed that enlargeosomes are (as expected) small vesicles ~80nm in diameter, that the endocytosis of the Ahnak-rich membrane occurs by a process distinct from the usual endocytoses; that endocytosis is not the only process by which recycling of the exocytized Ahnak-rich membrane occurs, the other being the shedding of vesicles to the extracellular space.

Finally, recent results have shown that the SNAREs involved in the enlargeosome exocytosis (VAMP4, SNAP23 and possibly syntaxin 6) are different from those specific of the classical neurosecretion. Based on these results we intend to choose a specific project for the student. At the moment the result that appears the most promissing is the identification of a protein exposed at the cytosolic surface of the enlargeosome membrane, the vSNARE VAMP4, that we intend to use also for the isolation of the organelle, necessary to investigate in detail a variety of processes, from the biogenesis to the exocytic discharge.

Another project could deal with the purification and the investigation of specific vesicles shed from the surface of many cells upon stimulation that our previous studies had shown to be bound by a membrane containing enlargeosome components and to include peculiar proteins. Vesicles such as these are interesting from many points of view: mechanisms of generation, precise composition,functional significance for intercellular communication etc.

Acquisition of neurosecretion competence
Recently, work carried out on the defective PC12 that has lead to the identification of REST as the general governor of the neurosecretory phenotype. Specifically we have found that the increase of REST in wt PC12 cells induces the decreased expression of vesicle/exocytosis gene expression; its decrease in defective PC12 cells induces the re-expression of these gene products, with re-appearance of the vesicles and of their discharge.

These results have opened a large number of research lines that deserve to be investigated. Among these are: the mechanisms controlling the expression of REST and its fluctuations in differentiated neurons, in neurosecretory cells and in astrocytes, a peculiar type of neurosecretory cells of great mportance in the brain; the role and the mechanisms of control of the REST modulatory protein, BHC80; the mechanisms, triggered by REST in the cell, in addition to the transcriptional repression; the role of REST repression in forms of pathology characterized by reductions in the activity of neurosecretory cells, beginning with type2 diabetes and with some forms of cancer (REST has been shown to play the role of anti-oncogene) ; the role of the repressor in the neurosecretion incompetence of non-nerve cell types. A choice among these issues could give the student the opportunity of an original and exciting research project.