Mervyn Monteiro (the author of this report) and colleagues described the identification and characterization of two different proteins that interact with presenilins in the yeast-2 hybrid interaction trap (Y2H). Stabler et al. (Abstract 1056) described the interaction of a calcium-binding-myristoylated protein with homology to calcineurin, which we have termed calmyrin, with the loop region of presenilin-2. Interestingly, calmyrin bound preferentially and with 10-fold greater affinity to the PS2-loop compared to the corresponding PS1-loop in Y2H assays. When coexpressed in HeLa cells, calmyrin and PS2 colocalized, and caused additive cell death.

Mah et al. (Abstract 1058) described the cloning of a novel ubitiquously expressed 66 kDa protein that interacted strongly with the C-terminal region of the presenilins in Y2H assays. A monospecific antibody raised against the novel protein reveals punctate vesicle-like staining throughout the cell. When the novel protein and PS2 are coexpressed the two proteins colocalize by double immunofluorescence microscopy. The novel protein has homology to genes of unknown function in yeast and Caenorhabditis elegans uncovered in the genome sequencing effort. The novel protein contains a ubiquitin-like motif. Many basic functions of this protein are still unknown, including its regulation and expression in AD.

Smine et al. (Abstract 2099) presented elegant biochemical and immunological data that the C-terminal region (residues 379-467) of PS1 binds the Go form of G-proteins selectively. PS1 and Go proteins coimmunoprecipitated, and the two proteins partially colocalized by double immunofluorescence microscopy. PS1 interaction with Go may be important in G-protein activation which they demonstrated, as expected, was Mg-dependent.—Mervyn Monteiro

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