Biomedical subjects

Eva Geuens

Publications and source records attributed to Eva Geuens.

5 recordsLinked to original sources

PubMed2006

Does neuroglobin protect neurons from ischemic insult? A quantitative investigation of neuroglobin expression following transient MCAo in spontaneously hypertensive rats.

Neuroglobin (NGB) is a recently characterized heme globin expressed primarily in retinal nerve cells and at very low levels in endocrine-active regions of vertebrate brains. When artificially over-expressed, NGB reduces the infarct size observed after transient Middle Cerebral Artery occlusion (tMCAo) in rats. This study addresses the post-ischemic NGB expression in vivo. Ten Spontaneously Hypertensive Rats (SHRs) were randomized to tMCAo (n = 6) or sham (n = 4), and euthanized 24 h later. NGB mRNA expression was determined by means of quantitative Reverse Transcription Polymerase Reaction (qRT-PCR). Thirteen animals subjected to either 90 min tMCAo (n = 7) or sham (n = 6) surgery, were euthanized 1 week after surgery. Post-ischemic expression of NGB and the neuronal marker NeuN was studied using free-floating immunohistochemistry. Design-based stereological quantification of NGB- and NeuN-positive cells in the striatum was performed using the optical fractionator. Significantly less NGB mRNA was expressed in the ischemic hemispheres of tMCAo animals after 24 h (P < or = 0.002). At the protein level, we found a significantly lower number of NGB- and NeuN-positive striatal neurons in tMCAo rats (P < or = 0.004). NGB expression was mainly confined to the hypothalamus and amygdala. Less than one out of every two thousand neurons expressed NGB in the striatum. In the ischemic territory we did not observe selective sparing of NGB expressing neurons. No significant change in the NGB/NeuN ratio was observed. Our data indicate that endogenous expressed NGB does not provide protection against ischemic injury induced by tMCAo in SHRs.

Amygdala↗

PubMed2004

Thr-E11 regulates O2 affinity in Cerebratulus lacteus mini-hemoglobin.

The mini-hemoglobin from Cerebratulus lacteus (CerHb) belongs to a class of globins containing the polar Tyr-B10/Gln-E7 amino acid pair that normally causes low rates of O2 dissociation and ultra-high O2 affinity, which suggest O2 sensing or NO scavenging functions. CerHb, however, has high rates of O2 dissociation (kO2 = 200-600 s(-1)) and moderate O2 affinity (KO2) approximately 1 microm(-1)) as a result of a third polar amino acid in its active site, Thr-E11. When Thr-E11 is replaced by Val, kO2 decreases 1000-fold and KO2 increases 130-fold at pH 7.0, 20 degrees C. The mutation also shifts the stretching frequencies of both heme-bound and photodissociated CO, indicating marked changes of the electrostatic field at the active site. The crystal structure of Thr-E11 --> Val CerHbO2 at 1.70 A resolution is almost identical to that of the wild-type protein (root mean square deviation of 0.12 A). The dramatic functional and spectral effects of the Thr-E11 --> Val mutation are due exclusively to changes in the hydrogen bonding network in the active site. Replacing Thr-E11 with Val "frees" the Tyr-B10 hydroxyl group to rotate toward and donate a strong hydrogen bond to the heme-bound ligand, causing a selective increase in O2 affinity, a decrease of the rate coefficient for O2 dissociation, a 40 cm(-1) decrease in nuCO of heme-bound CO, and an increase in ligand migration toward more remote intermediate sites.

Animals↗

PubMed2003

A globin in the nucleus!

Cytoglobin and neuroglobin are recently discovered members of the globin family. In situ hybridization localized neuroglobin mainly in brain and retina, while cytoglobin was expressed ubiquitously in all analyzed tissues. In the present study, polyclonal antibodies were raised against both proteins and the distribution of them was studied by immunocytochemistry at tissue and subcellular level. Cytoglobin immunoreactivity was uniformly distributed and found in all tissues studied. At the subcellular level, cytoglobin immunoreactivity was exclusively detected in the cell nucleus. In contrast, neuroglobin immunoreactivity was detected in specific brain regions with varying intensities and in the islet of Langerhans in the pancreas. The immunoreactivity was restricted to the cytoplasm of neurons and endocrine beta cells. The nuclear localization of cytoglobin opens new perspectives for possible function(s) of globin-folded proteins as transcriptional regulators.

Animals↗

PubMed2002

The 109 residue nerve tissue minihemoglobin from Cerebratulus lacteus highlights striking structural plasticity of the alpha-helical globin fold.

A very short hemoglobin (CerHb; 109 amino acids) binds O(2) cooperatively in the nerve tissue of the nemertean worm Cerebratulus lacteus to sustain neural activity during anoxia. Sequence analysis suggests that CerHb tertiary structure may be unique among the known globin fold evolutionary variants. The X-ray structure of oxygenated CerHb (R factor 15.3%, at 1.5 A resolution) displays deletion of the globin N-terminal A helix, an extended GH region, a very short H helix, and heme solvent shielding based on specific aromatic residues. The heme-bound O(2) is stabilized by hydrogen bonds to the distal TyrB10-GlnE7 pair. Ligand access to heme may take place through a wide protein matrix tunnel connecting the distal site to a surface cleft located between the E and H helices.

Amino Acid Sequence↗

PubMedDate not supplied

Genome-wide analysis of the globin gene family of C. elegans.

The aim of our study was to annotate sequences for 35 putative globins from the nematode Caenorhabditis elegans. All these proteins are expressed, but seven of these differ from the gene predictions in Wormbase. The entire polypeptide sequences for 31 genes and the core globin domain of four proteins were confirmed or corrected. All core globin domains were aligned manually following a procedure that was designed to fit the putative sequences to the crystal structure based alignment of 56 known globin crystal structures. Neighbor-joining analysis of the resulting alignment showed that the majority of these globins are very divergent from each other, possibly suggesting a long evolutionary divergence. The surprisingly high number and low sequence conservation of putative globins in this small organism urges a detailed functional analysis.

Animals↗