Symposia of the Society for Experimental Biology最新文献

It is clear that the roles of apoptosis in the interactions between the parasite and their non-mammalian hosts are multifaceted and highly dependent on individual associations between the two organisms involved. Whilst there are instances where both organisms appear to gain from the apoptotic mechanism induced, in the majority of cases apoptosis appears to favour only one of the parties. In the instances when the parasite benefits, the apoptosis has been related to infectivity and virulence, an interruption of the killing mechanism of the host, and liberation of the pathogen. However, there are occasions where the apoptotic process benefits the host, as controlled cell death has been associated with limiting the pathogen population, parasite migration within the host and, in some instances, actually killing the invading organism. Apoptosis thus appears to play several fundamental roles within the host-parasite relationship which is ultimately reflected in an effect on the host population either mediated through an alteration in host fecundity or reduction in host numbers. The next decade promises to be both exciting and productive with respect to our knowledge of the relationship between apoptosis in non-mammalian animals and infection. Over the last few years the information obtained from studies on the apoptotic process in mammals and invertebrates (i.e. C. elegans and Drosophila) have been effectively used to increase our understanding of the apoptotic process in other animals such as insects, fish and amphibians. Such knowledge has paved the way for extensive studies on the effect of infections to be carried out.

Compared to research in the animal field, the plant NE has been clearly under-investigated. The available data so far indicate similarities as well as striking differences that raise interesting questions about the function and evolution of the NE in different kingdoms. Despite a seemingly similar structure and organization of the NE, many of the proteins that are integral components of the animal NE appear to lack homologues in plant cells. The sequencing of the Arabidopsis genome has not led to the identification of homologues of animal NE components, but has indicated that the plant NE must have a distinct protein composition different from that found in metazoan cells. Besides providing a selective barrier between the nucleoplasm and the cytoplasm, the plant NE functions as a scaffold for chromatin but the scaffolding components are not identical to those found in animal cells. The NE comprises an MTOC in higher plant cells, a striking difference to the organization of microtubule nucleation in other eukaryotic cells. Nuclear pores are present in the plant NE, but identifiable orthologues of most animal and yeast nucleoporins are presently lacking. The transport pathway through the nuclear pores via the action of karyopherins and the Ran cycle is conserved in plant cells. Interestingly, RanGAP is sequestered to the NE in plant cells and animal cells, yet the targeting domains and mechanisms of attachment are different between the two kingdoms. At present, only a few proteins localized at the plant NE have been identified molecularly. Future research will have to expand the list of known protein components involved in building a functional plant NE.

What can be concluded about lamin dynamics? a. While the nuclear lamina forms a tight network of proteins, individual lamina members, such as the lamin C proteins, are only partially bound to the lamina. b. A prominent pool of nucleoplasmic lamins exists in most cells, which interacts with intranuclear structures (DNA? Histones? Replication and/or transcription complexes?) in a dynamic fashion. c. During mitosis lamins do not play a key role in the initial reformation of the nuclear envelope. However, they are important for the correct functioning of the nucleus immediately after mitosis. Many questions remain unanswered, although nuclear lamins have been studied at different levels for over 20 years. We have only just begun to understand their crucial role in several cellular processes. Some of the important questions that still remain are: a. The function of intranuclear lamin foci. Are these native nuclear structures (nuclear channels/tubules) and do they play a role in replication and transcription? b. The function of the nucleoplasmic veil of lamins. Are these molecules only temporarily bound to intranuclear structures as a result of affinity to chromosomes or nuclear proteins, or is there a functional interaction with these molecules? c. The extent to which lamin molecules add to nuclear membrane organisation. Do these molecules play a key role in keeping the membrane intact and the nucleus functional, or are they only one of many supportive component of the nuclear membrane?