| || |
Phone (+351) 214469437 | Extension 1437
Most mammalian proteins contain covalently linked oligosaccharides. The initial step in N-glycosylation occurs in the endoplasmic reticulum and consists of the transfer of a precursor oligosaccharide to the nascent polypeptide chain. Processing of this precursor oligosaccharide by several glycosidases and glycosyltransferases in the endoplasmic reticulum and Golgi apparatus results in the final oligosaccharide chain. O-glycosylation occurs in the Golgi and consists of the sequential addition of monosaccharide residues to the protein. Peripheral fucosyltransferases are late acting glycosyltransferases that synthesize the carbohydrate adhesion determinants of the Lewis type.
Protein glycosylation depends on several factors including the three-dimensional structure of the protein and the set of glycosidases and glycosyltransferases of the host cell. Oligosaccharides have been shown to be important for several processes including protein folding, intracellular transport, cell-cell interactions and signalling.
The following carbohydrate structures have been found in neuronal tissue: the fucosylated determinant Lewis X, peripheral alpha2-linked fucose, polysialylation, the HNK-1 epitope, bissecting GlcNAc and O-mannosylation among others. We have previously obtained evidence that supports the importance of the determinant Lewis X in neurite outgrowth. Furthermore, it has been found in synaptic sites of glutamatergic neurons. We are currently studying the Lewis X determinant in neuronal tissue with the aims of elucidating its regulation (e.g., interplay with the cell adhesion molecule L1) and functional role, and identifying possible lectin receptors. On the other hand, we have studied the substrate specificity of fucosyltransferase 9, which is predominantly expressed in the brain, as well as other fucosyltransferases, and used them to produce fucosylated compounds in vitro in order to study their biological effect on our cellular systems.
Another line of research in the laboratory consists of the analysis of glycoproteins from the plasma and cerebrospinal fluid of patients with the neurodegenerative disease Amyotrophic Lateral Sclerosis, to identify possible biomarkers. Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of the motor neurons. At present there are no validated biomarkers of the disease, which would be helpful for the diagnosis and the testing of potential therapeutic compounds.
- Ricardo Gouveia, Post-doctoral fellow
- Eda Machado, Ph.D. student
- Cristina Escrevente, Ph.D. student
- Rita Carilho, Post-graduate student (BI)
- Gouveia, R., Kandzia, S., Conradt, H.S., Costa, J. (2010) N-glycosylation of human cell adhesion molecule L1 expressed in insect cells using the stable expression system. Effect of dimethyl sulfoxide. J. Biotechnol. 145, 130-138.
- Costa, J., Gomes, C., de Carvalho, M. (2010) Diagnosis, Pathogenesis and Therapeutic Targets in Amyotrophic Lateral Sclerosis. CNS Neurol Disord Drug Targets 9, 764-78.
- Machado, E., Kandzia, S., Carilho, R., Altevogt, P., Conradt, H.S., Costa, J. (2011) N-Glycosylation of total cellular glycoproteins from the human ovarian carcinoma SKOV3 cell line and of recombinantly expressed human erythropoietin . Glycobiology 21, 376-86.
For further information visit the laboratory's website
A maior parte das proteínas de células de mamífero contém oligossacáridos ligados covalentemente. A glicosilação de proteínas secretadas ou de membrana ocorre no retículo endoplasmático e no complexo de Golgi e envolve a acção de várias glicosiltransferases e glicosidases. A glicosilação proteica apresenta características específicas associadas ao organismo, ao tecido e à célula.
Um dos projectos que desenvolvemos no laboratório consiste no estudo da glicosilação de tecido neuronal, sua regulação e sua relevância biológica. Outro projecto consiste na análise de glicoproteínas de plasma e líquido cefalorraquidiano de pacientes com a doença neurodegenerativa Esclerose Lateral Amiotrófica, com vista à identificação de um biomarcador da doença.