Glycosylation of Twisted Gastrulation is Required for BMP Binding and Activity during Craniofacial Development

Twisted gastrulation (TWSG1) is a conserved, secreted glycoprotein that modulates signaling of bone morphogenetic proteins (BMPs) in the extracellular space. Deletion of exon 4 of mouse Twsg1 (mTwsg1) is associated with significant craniofacial defects. However, little is understood about the biochemical properties of the corresponding region of the protein. We have uncovered a significant role for exon 4 sequences as encoding the only two glycosylation sites of the mTWSG1 protein. Deletion of the entire exon 4 or mutation of both glycosylation sites within exon 4 abolishes glycosylation of mTWSG1. Importantly, we find that constructs with mutated glycosylation sites have significantly reduced BMP binding activity. We further show that glycosylation and activity of TWSG1 recombinant proteins vary markedly by cellular source. Non-glycosylated mTWSG1 made in E. coli has both reduced affinity for BMPs, as shown by surface plasmon resonance analysis, and reduced BMP inhibitory activity in a mandibular explant culture system compared to glycosylated proteins made in insect cells or murine myeloma cells. This study highlights an essential role for glycosylation in Twisted gastrulation action

The neurotoxin 1-methyl-4-phenylpyridinium (MPP+) alters hippocampal excitatory synaptic transmission by modulation of the GABAergic system

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces Parkinson’s disease (PD)-like symptoms following administration to mice, monkeys and humans. A common view is that MPTP is metabolized to 1-methyl-4-phenylpyridinium ion (MPP+) to induce its neurodegenerative effects on dopaminergic neurons in the substantia nigra. Moreover, the hippocampus contains dopaminergic fibers, which are projecting from the ventral tegmental area, substantia nigra and pars compacta and contain the whole machinery required for dopamine synthesis making them sensitive to MPTP and MPP+. Here we present data showing that acute bath-application of MPP+ elicited a dose-dependent facilitation followed by a depression of synaptic transmission of hippocampal Schaffer collaterals-CA1 synapses in mice. The effects of MPP+ were not mediated by D1/D5- and D2-like receptor activation. Inhibition of the dopamine transporters (DAT) did not prevent but increased the depression of excitatory postsynaptic field potentials. In the search for a possible mechanism, we observed that MPP+ reduced the appearance of polyspikes in population spikes recorded in str. pyramidale and increased the frequency of miniature inhibitory postsynaptic currents. The acute effect of MPP+ on synaptic transmission was attenuated by co-application of a GABAA receptor antagonist. Taking these data together, we suggest that MPP+ affects hippocampal synaptic transmission by enhancing some aspects o

Suberoylanilide Hydroxamic Acid, A Histone Deacetylase Inhibitor, Attenuates Postoperative Cognitive Dysfunction in Aging Mice

Postoperative cognitive dysfunction (POCD) is a recognized clinical entity characterized with cognitive deficits after anesthesia and surgery, especially in aged patients. Previous studies have shown that histone acetylation plays a key role in hippocampal synaptic plasticity and memory formation. However, its role in POCD remains to be determined. Here, we show that suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, attenuates POCD in aging Mice. After exposed to the laparotomy, a surgical procedure involving an incision into abdominal walls to examine the abdominal organs, 16- but not 3-month old male C57BL/6 mice developed obvious cognitive impairments in the test of long-term contextual fear conditioning. Intracerebroventricular (i.c.v.) injection of SAHA at the dose of (20 μg/2 μl) 3 hours before and daily after the laparotomy restored the laparotomy-induced reduction of hippocampal acetyl-H3 and acetyl-H4 levels and significantly attenuated the hippocampus-dependent long-term memory impairments in 16-month old mice. SAHA also reduced the expression of cleaved caspase-3, inducible nitric oxide synthase and N-methyl-D-aspartate receptor-calcium/calmodulin dependent kinase II pathway, and increased the expression of brain-derived neurotrophic factor, synapsin 1, and postsynaptic density 95. Taken together, our data suggest that the decrease of histone acetylation contributes to POCD and may serve as a target to improve the neurological outcome of POCD