Human-Specific ARHGAP11B Acts in Mitochondria to Expand Neocortical Progenitors by Glutaminolysis.

The human-specific gene ARHGAP11B is preferentially expressed in neural progenitors of fetal human neocortex and increases abundance and proliferation of basal progenitors (BPs), which have a key role in neocortex expansion. ARHGAP11B has therefore been implicated in the evolutionary expansion of the human neocortex, but its mode of action has been unknown. Here, we show that ARHGAP11B is imported into mitochondria, where it interacts with the adenine nucleotide translocase (ANT) and inhibits the mitochondrial permeability transition pore (mPTP).

FlexiBAC: a versatile, open-source baculovirus vector system for protein expression, secretion, and proteolytic processing.

Background: Baculovirus-mediated expression in insect cells is a powerful approach for protein production. However, many existing methods are time-consuming, offer limited options for protein tagging, and are unsuitable for secreted proteins requiring proteolytic maturation, such as TGF-β family growth factors.

Results: To overcome the limitations of traditional baculovirus expression systems, we engineered "FlexiBAC".

Molecular parallelism in fast-twitch muscle proteins in echolocating mammals.

Detecting associations between genomic changes and phenotypic differences is fundamental to understanding how phenotypes evolved. By systematically screening for parallel amino acid substitutions, we detected known as well as novel cases (Strc, Tecta, and Cabp2) of parallelism between echolocating bats and toothed whales in proteins that could contribute to high-frequency hearing adaptations. Our screen also showed that echolocating mammals exhibit an unusually high number of parallel substitutions in fast-twitch muscle fiber proteins.

Stability of proICA512/IA-2 and its targeting to insulin secretory granules require β4-sheet-mediated dimerization of its ectodomain in the endoplasmic reticulum.

The type 1 diabetes autoantigen ICA512/IA-2/RPTPN is a receptor protein tyrosine phosphatase of the insulin secretory granules (SGs) which regulates the size of granule stores, possibly via cleavage/signaling of its cytosolic tail. The role of its extracellular region remains unknown. Structural studies indicated that β2- or β4-strands in the mature ectodomain (ME ICA512) form dimers in vitro.

Purification of tubulin from porcine brain.

Microtubules, polymers of the heterodimeric protein αβ-tubulin, give shape to cells and are the tracks for vesicle transport and chromosome segregation. In vitro assays to study microtubule functions and their regulation by microtubule-associated proteins require the availability of purified αβ-tubulin. In this chapter, we describe the process of purification of heterodimeric αβ-tubulin from porcine brain.

Biogenesis of secretory granules.

Secretory granules of neuroendocrine cells store and release peptide hormones and neuropeptides in response to various stimuli. Generation of granules from the Golgi complex involves the aggregation of cargo proteins and their sorting from non-regulated secretory molecules. Recent findings on knockout mice lacking individual granule constituents have challenged the hypothesis that an 'essential' protein for the assembly of these organelles exists, while studies on polypyrimidine tract-binding protein and ICA512/IA-2 have provided insight into the mechanisms for adjusting granule production in relation to stimulation and secretory activity.

The small chemical vacuolin-1 inhibits Ca(2+)-dependent lysosomal exocytosis but not cell resealing.

Resealing after wounding, the process of repair following plasma membrane damage, requires exocytosis. Vacuolins are molecules that induce rapid formation of large, swollen structures derived from endosomes and lysosomes by homotypic fusion combined with uncontrolled fusion of the inner and limiting membranes of these organelles. Vacuolin-1, the most potent compound, blocks the Ca(2+)-dependent exocytosis of lysosomes induced by ionomycin or plasma membrane wounding, without affecting the process of resealing.

Polypyrimidine tract-binding protein promotes insulin secretory granule biogenesis.

Pancreatic beta-cells store insulin in secretory granules that undergo exocytosis upon glucose stimulation. Sustained stimulation depletes beta-cells of their granule pool, which must be quickly restored. However, the factors promoting rapid granule biogenesis are unknown.

Regulated exocytosis: a novel, widely expressed system.

Electrophysiological studies in some secretory and non-secretory cells have identified an extensive form of calcium-induced exocytosis that is rapid (hundreds of milliseconds), insensitive to tetanus toxin and distinct from regulated secretion. We have now identified a marker of the process, desmoyokin-AHNAK, in a clonal derivative of the neuronal cell line, PC12. In resting cells, desmoyokin-AHNAK is localized within the lumen of specific vesicles, but appears on the cell surface during stimulation.