Drosophila rugose is a functional homolog of mammalian Neurobeachin and affects synaptic architecture, brain morphology, and associative learning.

Neurobeachin (Nbea) is implicated in vesicle trafficking in the regulatory secretory pathway, but details on its molecular function are currently unknown. We have used Drosophila melanogaster mutants for rugose (rg), the Drosophila homolog of Nbea, to further elucidate the function of this multidomain protein. Rg is expressed in a granular pattern reminiscent of the Golgi network in neuronal cell bodies and colocalizes with transgenic Nbea, suggesting a function in secretory regulation. In contrast to Nbea(-/-) mice, rg null mutants are viable and fertile and exhibit aberrant associative odor learning, changes in gross brain morphology, and synaptic architecture as determined at the larval neuromuscular junction. At the same time, basal synaptic transmission is essentially unaffected, suggesting that structural and functional aspects are separable. Rg phenotypes can be rescued by a Drosophila rg+ transgene, whereas a mouse Nbea transgene rescues aversive odor learning and synaptic architecture; it fails to rescue brain morphology and appetitive odor learning. This dissociation between the functional redundancy of either the mouse or the fly transgene suggests that their complex composition of numerous functional and highly conserved domains support independent functions. We propose that the detailed compendium of phenotypes exhibited by the Drosophila rg null mutant provided here will serve as a test bed for dissecting the different functional domains of BEACH (for beige and human Chediak-Higashi syndrome) proteins, such as Rugose, mouse Nbea, or Nbea orthologs in other species, such as human.

Sexual stage adhesion proteins form multi-protein complexes in the malaria parasite Plasmodium falciparum.

The sexual phase of the malaria parasite Plasmodium falciparum is accompanied by the coordinated expression of stage-specific adhesive proteins. Among these are six secreted proteins with multiple adhesion domains, termed P. falciparum LCCL domain-containing protein (PfCCp) proteins, which are expressed in the parasitophorous vacuole of the differentiating gametocytes and which are later associated with macrogametes. Although the majority of the PfCCp proteins are implicated in parasite development in the mosquito vector, their functions remain unknown. In the present study we investigated the molecular interactions between the PfCCp proteins during gametocyte development and emergence. Using five different gene-disruptant parasite lines, we show that the lack of one PfCCp protein leads to the loss of other PfCCp family members. Co-immunoprecipitation assays on gametocyte lysates revealed formation of complexes involving all PfCCp proteins, and affinity chromatography co-elution binding assays with recombinant PfCCp domains further indicated direct binding between distinct adhesion domains. PfCCp-coated latex beads bind to newly formed macrogametes but not to gametocytes or older macrogametes 6 or 24 h post-activation. In view of these data, we propose that the PfCCp proteins form multi-protein complexes that are exposed during gametogenesis, thereby mediating cell contacts of macrogametes.

Umbrea, a chromo shadow domain protein in Drosophila melanogaster heterochromatin, interacts with Hip, HP1 and HOAP.

Drosophila melanogaster HP1-interacting protein (Hip) is a partner of heterochromatin protein 1 (HP1) and is involved in transcriptional epigenetic gene silencing and the formation of heterochromatin. Recently, it has been shown that HP1 interacts with the telomere capping factor HP1/ORC (origin recognition complex)-associated protein (HOAP). Telomeres, complexes of DNA and proteins at the end of linear chromosomes, have been recognized to protect chromosome ends from degradation and fusion events. Both proteins are located at telomeres and prevent telomere fusions. Here, we report the identification and characterization of the Hip-interacting protein Umbrea. We found that Umbrea interacts directly with Hip, HP1 and HOAP in vitro. Umbrea, Hip and HP1 are partners in a protein complex in vivo and completely co-localize in the pericentric heterochromatin and at telomeres. Using a Gal4-induced RNA interference system, we found that after depletion of Umbrea in salivary gland polytene chromosomes, they exhibit multiple telomeric fusions. Taken together, these results suggest that Umbrea cooperates with Hip, HP1 and HOAP and plays a functional role in mediating normal telomere behaviour in Drosophila.

PfCCp proteins of Plasmodium falciparum: gametocyte-specific expression and role in complement-mediated inhibition of exflagellation.

The sexual phase of the malaria parasite Plasmodium falciparum is essential for transmission of the disease and is accompanied by the co-ordinated expression of sexual stage proteins. Six of these proteins belong to a highly conserved apicomplexan family of multi-domain adhesion proteins, termed PfCCps. PfCCp1, PfCCp2 and PfCCp3 are co-dependently expressed in the parasitophorous vacuole associated with the gametocyte plasma membrane. PfCCp2 and PfCCp3 also play an essential role for parasite development in the mosquito. We show that the six PfCCp proteins are expressed in stages II-V of gametocytogenesis as well as during early gamete formation. The proteins are expressed in association with the surface of both male and female gametocytes and macrogametes, but are not present in exflagellating microgametes. Further, the newly described protein PfCCp4 co-localizes with the transmission blocking candidate Pfs230, with which it forms a protein complex. In contrast to the phenotypes that are observed following targeted gene disruption of PfCCp2, PfCCp3 or Pfs230, the lack of PfCCp4 expression does not inhibit parasite development in the mosquito vector. This indicates a non-essential role for this protein during parasite transmission. Exflagellation assays revealed that antibodies directed against distinct domains of PfCCp1 through PfCCp4 and PfFNPA support a complement-mediated decrease in gametocyte emergence. We conclude that the six PfCCp proteins are specifically expressed during gametocytogenesis and gamete formation, and that select members may represent prospective candidates for transmission blocking vaccines.