La percepci\u00f3 visual s’inicia amb la captaci\u00f3 de la llum per les c\u00e8l\u00b7lules fotoreceptor de la retina, bastons i cons, que mitjan\u00e7ant una cascada enzim\u00e0tica d’amplificaci\u00f3 la converteixen en un senyal el\u00e8ctric que es transmet a a neurones d’ordre superior i al cervell.<\/p>\n
Les c\u00e8l\u00b7lules fotoreceptor mesuren i transmeten en cada moment la intensitat de llum en cada punt del camp visual. Ho fan amb una sensibilitat extraordin\u00e0ria, alhora que amb la capacitat de modular aquesta sensibilitat depenent de la llum ambiental. Aquesta capacitat de modulaci\u00f3 \u00e9s essencial per poder manejar-se en el m\u00f3n natural, en qu\u00e8 la llum ambiental varia constantment.<\/p>\n
La capacitat de modular la resposta a la llum depenent de la llum de fons, l’adaptaci\u00f3 a la llum, resideix en un senyal de calci. La llum, a m\u00e9s de canviar el potencial de membrana dels fotoreceptors, produeix una baixada de calci en la c\u00e8l\u00b7lula. Aquesta baixada de calci coordina un senyal de retrorregulaci\u00f3 de la cascada enzim\u00e0tica de fototransducci\u00f3 a diversos nivells, que contraresta l’amplificaci\u00f3. Aquest senyal de regulaci\u00f3 est\u00e0 intervinguda per prote\u00efnes d’uni\u00f3 a calci (neuronal calcium sensor proteins, NCS), entre les quals es troben les prote\u00efnes activadores de l’activitat guanilat ciclasa o GCAPs, per les seves sigles en angl\u00e8s.<\/p>\n
La l\u00ednia d’investigaci\u00f3 dirigida per Ana M\u00e9ndez a l’Idibell t\u00e9 com un dels seus objectius caracteritzar les bases moleculars de l’adaptaci\u00f3 a la llum, el paper de les prote\u00efnes GCAP en aquest proc\u00e9s, i entendre com errors gen\u00e8tics a aquest nivell condueixen a diferents formes de ceguesa heredit\u00e0ria. Un treball recent del grup que es publica ara a PLoS Genetics, revela que quan falla la transici\u00f3 conformacional en una d’aquestes prote\u00efnes sensors de calci en fotoreceptors, GCAP2, de la forma “lliure de Ca2 +” a la forma “unida a Ca2 +”, es desencadena una degeneraci\u00f3 retinal severa que difereix mecan\u00edsticament de la distr\u00f2fia retinal associada a errors gen\u00e8tics en GCAP1.<\/p>\n
L’estudi demostra com en el cas de GCAP2 la prote\u00efna en la seva forma lliure de calci no es distribueix al compartiment sensorial, sin\u00f3 que s’acumula en el segment intern de la c\u00e8l\u00b7lula despr\u00e9s de ser fosforilada i retinguda per la seva uni\u00f3 a 14-3-3. \u00c9s aquesta acumulaci\u00f3 de la prote\u00efna en el segment erroni el que comporta a la mort cel\u00b7lular. L’estudi revela un nou mecanisme fisiol\u00f2gic de control de la distribuci\u00f3 de GCAP2 a la c\u00e8l\u00b7lula \u00edntimament lligat a malaltia, en el sentit que una desregulaci\u00f3 greu d’aquest mecanisme condueix a una degeneraci\u00f3 retinal r\u00e0pida en models murins.<\/p>\n
L’estudi proposa que aquest mecanisme podria contribuir a explicar la patologia d’aquelles cegueses causades no nom\u00e9s per mutacions en GCAP2 que alterin la seva afinitat d’uni\u00f3 a calci; sin\u00f3 tamb\u00e9 per exposicions prolongades a llum intensa, o per mutacions en gens que resultin en una situaci\u00f3 equivalent a l’exposici\u00f3 a llum intensa, b\u00e9 per causar activaci\u00f3 constitutiva o per causar defectes en terminaci\u00f3, els globalment referits com desordres “llum-equivalent”.<\/p>\n","protected":false},"excerpt":{"rendered":"
La percepci\u00f3 visual s’inicia amb la captaci\u00f3 de la llum per les c\u00e8l\u00b7lules fotoreceptor de la retina, bastons i cons, que mitjan\u00e7ant una cascada enzim\u00e0tica d’amplificaci\u00f3 la converteixen en un senyal el\u00e8ctric que es transmet a a neurones d’ordre superior i al cervell. Les c\u00e8l\u00b7lules fotoreceptor mesuren i transmeten en cada moment la intensitat de […]<\/p>\n","protected":false},"author":6,"featured_media":8327,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"no-sidebar","site-content-layout":"page-builder","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"default","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"footnotes":""},"categories":[1,347],"tags":[],"publishpress_future_action":{"enabled":false,"date":"2024-05-11 18:13:27","action":"change-status","newStatus":"draft","terms":[],"taxonomy":"category"},"_links":{"self":[{"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/posts\/8326"}],"collection":[{"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/comments?post=8326"}],"version-history":[{"count":0,"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/posts\/8326\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/media\/8327"}],"wp:attachment":[{"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/media?parent=8326"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/categories?post=8326"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/idibell.cat\/wp-json\/wp\/v2\/tags?post=8326"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}