Capping protein: new insights into mechanism and regulation

Temporal and spatial control of the actin cytoskeleton are crucial for a range of eukaryotic cellular processes. Capping protein (CP), a ubiquitous highly conserved heterodimer, tightly caps the barbed (fast-growing) end of the actin filament and is an important component in the assembly of various actin structures, including the dynamic branched filament network at the leading edge of motile cells. New research into the molecular mechanism of how CP interacts with the actin filament in vitro and the function of CP in vivo, including discoveries of novel interactions of CP with other proteins, has greatly enhanced our understanding of the role of CP in regulating the actin cytoskeleton.     

Mitochondrial complex I: new insights from inhibitor assays

Summary The NADH:ubiquinone oxidoreductase (complex I) of the mitochondrial respiratory chain is by far the most complicated of the proton-translocating enzymes involved in the oxidative phosphorylation. Many clues regarding both electron transfer and proton translocation are still unknown. In this sense, inhibitor assays are relevant and useful pieces for elaborating a suitable model to explain the elusive bioenergetic mechanism of this enzyme. This short review presents the most recent advances in inhibitor studies and highlights the major controversies.Abbreviations ACG annonaceous acetogenin - MPP⁺ methylphenyl-pyridinium     

Mitochondrial uncoupling proteins: new insights from functional and proteomic studies

Mitochondria are the major sites of ATP synthesis through oxidative phosphorylation, a process that is weakened by proton leak. Uncoupling proteins are mitochondrial membrane proteins specialized in inducible proton conductance. They dissipate the proton electrochemical gradient established by the respiratory chain at the expense of reducing substrates. Several physiological roles have been suggested for uncoupling proteins, including roles in the control of the cellular energy balance and in preventive action against oxidative stress. This review focuses on new leads emerging from comparative proteomics about the involvement of uncoupling protein in the mitochondrial physiology. A brief overview on uncoupling proteins and on proteomics applied to mitochondria is also presented herein.     

The Fat and Warts signaling pathways: new insights into their regulation, mechanism and conservation

A cassette of cytoplasmic Drosophila tumor suppressors, including the kinases Hippo and Warts, has recently been linked to the transmembrane tumor suppressor Fat. These proteins act within interconnected signaling pathways, the principal functions of which are to control the growth and polarity of developing tissues. Recent studies have enhanced our understanding of the basis for signal transduction by Fat and Warts pathways, including the identification of a DNA-binding protein at the end of the pathway, have established the conservation of Fat and Warts signaling from flies to mammals, and have given us new insights into their regulation and biological functions.     

Mitochondrial tyrosine phosphoproteome: new insights from an up-to-date analysis

Tyrosine phosphorylation is a newcomer in the mitochondrial signaling and is currently emerging as an important mechanism for regulating mitochondrial processes. But to what extent? By analyzing an updated draft of the mitochondrial tyrosine phosphoproteome, the following observations can be drawn: more than a hundred mitochondrial proteins undergo tyrosine phosphorylation, phosphotyrosine proteins are distributed in each of the submitochondrial compartments, and mitochondrial tyrosine phosphorylated proteins are involved in a variety of functions as metabolism (electron transport chain, Krebs cycle, fatty acid and amino acid metabolism), solute and protein transport, mitochondrial translation machinery, quality protein assessment, oxidative stress, apoptosis, fission, and other. This large and varied collection suggests that tyrosine phosphorylation could be a widespread mechanism in modulating mitochondrial functions. Moreover the in silico model is here used to explore potential effects of tyrosine phosphorylation on selected mitochondrial proteins pointing out some future perspectives in this field.     

Mitochondrial DNA analysis provides new insights into the origin of the Chinese domestic goat

Many studies have focused on modern goats, however, few reports focused on origin and genetic structure of Chinese ancient goats. In this study, we analyzed the 289-bp fragment of mitochondrial DNA (mtDNA) control region from 14 Chinese ancient goats excavated from two archaeological sites in Inner Mongolia, China dating back about 2500 years. 10 haplotypes were successfully obtained from the 14 ancient goats. Phylogenetic analysis revealed the multiple maternal origins of Chinese domestic goats, three mtDNA lineages A, B, and D were identified in the Chinese ancient individuals, in which lineage A was predominant (70%), lineages B was moderate (20%), and lineage D was present at low frequency (10%). The network analysis showed that lineage B was subdivided into two subgroups B1 and B2. One of the Chinese ancient goats shared the founder haplotype in the center of subgroup B1, and the shared sequences of the founder haplotypes of subgroups B1 and B2 distributed mainly in China. These results implied that lineage B including subgroups B1 and B2 probably originated from China, and further supported the hypothesis that China may be one of the goat domestication centers. In addition, the analysis of shared sequences indicated that the ancient goats from Inner Mongolia were closely genetically related to Chinese modern goats, suggesting that the ancient goats from Inner Mongolia had the genetic contribution to Chinese modern goats.     

Phosphoproteomics: new insights into cellular signaling

Developments in the field of phosphoproteomics have been fueled by the need simultaneously to monitor many different phosphoproteins within the signaling networks that coordinate responses to changes in the cellular environment. This article presents a brief review of phosphoproteomics with an emphasis on the biological insights that have been derived so far.     

Closing the loops: new insights into the role and regulation of actin during cell polarization

In this review, we summarize recent results on the understanding of actin organization and cell polarization with an emphasis on the critical role of actin during this process. We first report on the advances made in understanding the function and mechanism of formin family proteins in the nucleation of actin filaments. We also discuss how formins and other regulators of actin dynamics are thought to be involved in the generation of cell polarity. In the second part we discuss new findings indicating that, rather than using a linear pathway from signal transduction to cytoskeleton re-organization, cell polarity is established through bidirectional interplay between these processes. We describe the various types of feedback loops identified and point out common schemes. Finally we briefly summarize the emerging role of actinlike proteins in the generation of polarity in prokaryotes that implies an early origin of actin's role in cell polarity.