Biographie / Biography
After his graduate studies in biophysics at Université du Québec à Trois-Rivières (UQTR), Christian Salesse was a postdoctoral fellow at the Johannes Gutenberg Universität in Mainz (Germany). He then became an assistant professor at UQTR in 1990 and full professor in 1998. He moved to the Université Laval in 2002 as the head of the ophthalmology research unit at the Centre de recherche du CHUL as well as the head of research of the department of ophthalmology. He was a Junior 1, Junior 2, Senior and National FRQS research fellow between 1990 and 2006. He moved to the Hôpital du St-Sacrement of the Centre de recherche du CHU de Québec-Université Laval in 2011 as the head of the theme Santé de la vision until 2018. He was an invited professor for various periods of time at several universities (Montpellier, Rennes and Bordeaux in France, Lisbon in Portugal, Changchun in China).
Presentation
Metabolism of the visual cycle and the activity of lecithin retinol acyltransferase from the retinal pigment epithelium
Christian Salesse, Ph. D.
The visual cycle allows to regenerate the visual pigment of photoreceptors after light absorption. The chromophore of the visual pigments is a particular isomer (11-cis) of a derivative of vitamin A, bearing an aldehyde functional group (11-cis retinal, 11cRal). Light absorption leads to the isomerization of this chromophore to all-trans retinal (ATRal). Apo-opsins with no 11cRAL are not responsive to light. 11cRAL must thus be regenerated and recombined with apo-opsins to form light-sensitive visual pigments in photoreceptors. ATRal is thus first converted to all-trans retinol (ATRol) in photoreceptors by retinol dehydrogenase 8. ATRol is subsequently conveyed to the retinal pigment epithelium (RPE) where it will successively be converted to all-trans retinyl ester (ATRes) by the enzyme lecithin retinol acyltransferase (LRAT). The production of ATRes by LRAT needs to be coordinately controlled to sustain normal vision and to protect the retina from photodamage. This involves an uptake of ATRol from blood circulation by the RPE, which is further metabolized by LRAT. ATRes is a lipid-soluble and stable storage form of the visual chromophore in the retinosomes of the RPE. We have characterized the enzymatic activity of a truncated form of LRAT as well as that of mutants of LRAT leading to retinal degeneration. Values of dissociation constants of the ATRol substrate of LRAT have shown almost no difference between native LRAT and its mutants, thus suggesting that this binding is not altered by mutations.