Protein prenylation: more than just glue?

As with other lipid modifications of proteins, prenylation now appears to be critically important in the regulation of protein function. Recent research has led to an explosion of information concerning prenylation signals, prenyl transferase enzymes and the role of prenylation in protein-membrane interactions. Experiments have examined the role of prenylation in protein function and the results suggest that protein prenylation may be involved in facilitating proper subcellular localization, promoting protein-protein and protein-membrane interactions and regulating protein function.     

Presynaptic AMPA receptors: more than just ion channels?

AMPA receptor ion channels are of paramount importance for postsynaptic excitation. Several reports demonstrate that AMPA receptors are present in the presynaptic compartment and point to a role of these receptors in the modulation of presynaptic function. We discuss here the possibility that not only ion influx through the receptor, but also biochemical cascades, activated by ligand binding and independent from ion flux, might contribute to AMPA mediated presynaptic modulation.     

CD95: more than just a death factor?

The CD95 protein delivers crucial signals for lymphocyte death, and may also negatively regulate T-lymphocyte activation by preventing the influx of calcium ions from the cell's exterior. The block in calcium-ion influx occurs through the activation of acidic sphingomyelinase and the release of ceramide, a metabolite that can also induce cell death.     

Vascular patterning: xylem or phloem?

Xylem and phloem are the major conduits for the transport of water and solutes through the plant. Recent work has helped to elucidate the mechanisms that determine the identity and arrangement of these two tissues.     

Root patterning: does auxin provide positional cues?

Patterning of Arabidopsis roots is mediated by cell-cell interactions, information flowing from differentiated to immature cells. The plant growth regulator auxin has now been shown to be involved in organizing the distal end of the root apex, including the extent and pattern of cell division programs and specification of cell identity.     

Bacteriophages and pathogenicity: more than just providing a toxin?

An increasing number of pathogenicity factors carried by bacteriophages have been discovered. This review considers bacteriophage-bacterium interaction and its relation to disease processes. We discuss the search for new bacteriophage-associated pathogenicity factors, with emphasis on recent advances brought by the use of genomic sequence data and the techniques of genomic epidemiology.     

Is canalization more than just a beautiful idea?

The heat-shock protein 90 (Hsp90) is currently thought to buffer eukaryotic cells against perturbations caused by pre-existing cryptic genetic variation. A new study suggests that the buffering function of Hsp90 could instead be due to its repression of de novo transposon-mediated mutagenesis.     

Myelin Po-protein,more than just a structural protein?

The protein P0 has long been proposed to be responsible for the compact nature of peripheral myelin through interactions of both its extracellular and cytoplasmic domains. Recent studies support such a role for P0's extracellular region while more precise mapping of its adhesive domains are ongoing. As P0 is a member of the immunoglobulin gene superfamily and perhaps bears the closest similarity to the ancestral molecule of this whole family, these studies may also have more general implications for adhesive interactions. In addition, although long believed to be purely an inert, structural molecule, P0 has been reported to promote neurite outgrowth, which suggests a more dynamic role for this interesting molecule.     

Bacterial Type II protein export and pilus biogenesis: more than just homologies?

Protein export by Gram-negative bacteria requires devoted machineries to allow for the passage of hydrolytic enzymes and toxins through the cell envelope. The Type II export machinery has a number of distinct characteristics, which include its role as an extension of Sec-dependent secretion, its ability to recognize and export fully folded substrates efficiently and, perhaps most significantly, the relationship between a subset of its gene products with the Type IV pilus-biogenesis apparatus. An important question is whether we can extrapolate our knowledge, albeit limited, of Type IV pilus biogenesis to understand the structure and function of the Type II export apparatus. This and other questions relating to the energetics of assembly and specificity of the apparatus are addressed in this article.     

The voltage-gated calcium-channel β subunit: more than just an accessory

Voltage-gated Ca²⁺ channels (VGCCs) are involved in a number of excitatory processes in the cell that regulate muscle contraction, neurotransmitter release, gene regulation, and neuronal migration. They consist of a central pore-forming α₁ subunit together with a number of associated auxiliary subunits including a cytoplasmic β subunit. With the aid of X-ray crystallography, it has been found that the β subunits of VGCCs (β_2a, β₃, and β₄) interact strongly with the I–II loop of the pore-forming α₁ subunit. Here we discuss the potential interaction sites of β_1a with its α₁ subunit as well as the skeletal ryanodine receptor. We suggest that not only can β_1a interact with the α₁ subunit I–II loop, but more subtle interactions may be possible through the II–III loop via the β_1a SH3 domain. Such findings could have important implications with respect to EC coupling.     

Amyloid structures: much more than just a cross-β fold

Solving the amyloid puzzle requires an integrated use of structural and functional approaches.

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Synaptic plasticity in cephalopods; more than just learning and memory?

The outstanding behavioural capacity of cephalopods is underpinned by a highly sophisticated nervous system anatomy and neural mechanisms that often differ significantly from similarly complex systems in vertebrates and insects. Cephalopods exhibit considerable behavioural flexibility and adaptability, and it might be expected that this should be supported by evident cellular and synaptic plasticity. Here, we review what little is known of the cellular mechanisms that underlie plasticity in cephalopods, particularly from the point of view of synaptic function. We conclude that cephalopods utilise short-, medium-, and long-term plasticity mechanisms that are superficially similar to those so far described in vertebrate and insect synapses. These mechanisms, however, often differ significantly from those in other animals at the biophysical level and are deployed not just in the central nervous system, but also to a limited extent in the peripheral nervous system and neuromuscular junctions.     

Plant-endophyte-herbivore interactions: More than just alkaloids?

A recent paper by Rasmussen et al., (New Phytol 2007; 173:787–97) describes the interactions between Lolium perenne cultivars with contrasting carbohydrate content and the symbiotic fungal endophyte Neotyphodium lolii at different levels of nitrogen supply. In a subsequent study undertaken by Rasmussen et al., (Plant Physiol 2008; 146:1440–53) 66 metabolic variables were analysed in the same material, revealing widespread effects of endophyte infection, N supply and cultivar carbohydrate content on both primary and secondary metabolites. Here, we link insect numerical responses to these metabolic responses using multiple regression analysis.Key words: Neotyphodium lolii, Lolium perenne, high sugar grasses, metabolomics, insect herbivoresPasture grasses are often infected with symbiotic fungal endophytes and benefits for host plants arising out of these associations are generally ascribed to endophyte produced anti-herbivorous alkaloids. We tested the effects of (i) infection with three strains of endophytes differing in their alkaloid profiles, (ii) high vs. low nitrogen (N) supply, and (iii) ryegrass cultivars with high vs. control levels of water soluble carbohydrates (WSCs) on numerical insect responses (aphids, thrips, mites). A difference in WSC content between the cultivars had no significant effect on insect numbers, whereas high N compared to low N supply increased mites, thrips and alate Rhopalosiphum spp., but decreased apterous Rhopalosiphum spp. The effect of endophyte infection was strain dependant and differed for the different insects.A total of 66 metabolic variables of the same plants analysed prior to insect treatment were linked to insect responses using multiple regression analysis. One of the major conclusions to be drawn is that alkaloids are not always the most important factor influencing numerical insect responses which will also be determined by other metabolites, clearly indicating the importance of metabolomics type studies to point the way toward a mechanistic explanation of grass-endophyte-herbivore interactions.Grass species are often hosts of symbiotic clavicipitaceous endophytic fungi¹ residing in the apoplastic spaces of above ground plant parts and usually not causing any visible symptoms of infection.^2–4 These fungal symbionts confer protection from insect herbivory to their host plants through alkaloids,^5–8 some of which (ergovaline, lolitrem B) are also toxic to grazing mammals.^9,10 Natural endophyte strains lacking these mammalian toxins, but still retaining at least some of their insect deterring features, have been commercialized and are now widely used in ryegrass and tall fescue based pastures.^11,12     

Regenerative medicine for the treatment of spinal cord injury: more than just promises?

Spinal cord injury triggers a complex set of events that lead to tissue healing without the restoration of normal function due to the poor regenerative capacity of the spinal cord. Nevertheless, current knowledge about the intrinsic regenerative ability of central nervous system axons, when in a supportive environment, has made the prospect of treating spinal cord injury a reality. Among the range of strategies under investigation, cell‐based therapies offer the most promising results, due to the multifactorial roles that these cells can fulfil. However, the best cell source is still a matter of debate, as are clinical issues that include the optimal cell dose as well as the timing and route of administration. In this context, the role of biomaterials is gaining importance. These can not only act as vehicles for the administered cells but also, in the case of chronic lesions, can be used to fill the permanent cyst, thus creating a more favourable and conducive environment for axonal regeneration in addition to serving as local delivery systems of therapeutic agents to improve the regenerative milieu. Some of the candidate molecules for the future are discussed in view of the knowledge derived from studying the mechanisms that facilitate the intrinsic regenerative capacity of central nervous system neurons. The future challenge for the multidisciplinary teams working in the field is to translate the knowledge acquired in basic research into effective combinatorial therapies to be applied in the clinic.     

The ins and outs of tubulin acetylation: more than just a post-translational modification?

Microtubules are highly dynamic polymers of α/β tubulin heterodimers that play key roles in cell division and in organizing cell cytoplasm. Although they have been discovered more than two decades ago, tubulin post-translational modifications recently gained a new interest as their role was increasingly highlighted in neuron differentiation and neurodegenerative disorders. Here, we specifically focus on tubulin acetylation from its discovery to recent studies that provide new insights into how it is regulated in health and disease and how it impacts microtubule functions. Even though new mechanisms involving tubulin acetylation are regularly being uncovered, the molecular links between its location inside the microtubule lumen and its regulators and effectors is still poorly understood. This review highlights the emerging roles of tubulin acetylation in multiple cellular functions, ranging from cell motility, cell cycle progression or cell differentiation to intracellular trafficking and signalling. It also points out that tubulin acetylation should no longer be seen as a passive marker of microtubule stability, but as a broad regulator of microtubule functions.