Exploring alternative roles of visual arrestin 1 in photoreceptor synaptic regulation and deciphering the molecular pathway of retinal degeneration using mouse knockout technology.

摘要

In the G-protein-coupled receptor (GPCR) phototransduction cascade, visual Arrestin1 (Arr1) binds to and deactivates phosphorylated light-activated opsins, a process that is critical for effective recovery and normal vision. In this dissertation study, we discovered a novel synaptic interaction between Arr1 and N-ethylmaleimide sensitive factor (NSF) that is enhanced in a dark environment when photoreceptors are depolarized and the rate of exocytosis is elevated. In the photoreceptor synapse, NSF functions to sustain a higher rate of exocytosis, in addition to the compensatory endocytosis to retrieve and to recycle vesicle membrane and synaptic proteins. Not only does Arr1 bind to the junction of NSF N-terminal and first ATPase domains in an ATP-dependent manner, but Arr1 also enhances both NSF ATPase and NSF disassembly activities. In mouse retinas with no Arr1 expression, the expression levels of NSF and other synapse-enriched genes are markedly reduced and lead to a substantial decrease in the exocytosis rate. This study demonstrates a vital modulatory role of Arr1 in the photoreceptor synapse and provides key insights into the potential molecular mechanisms of inherited retinal diseases, such as Oguchi disease and Arr1-associated retinitis pigmentosa.;Arr1-/- mice develop a light-dependent retinal degeneration and a light-independent cone dystrophy. We observed increased terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), activation of phosphorylated signal transducer and activator of transcription 3 (pSTAT3) in the Janus kinase (JAK)-STAT3 pathway, reactive gliosis, and cone dystrophy in Arr1-/- mice. To further explore the molecular pathways leading to Arr1-/--related light-independent cone dystrophy, we compared controls and Arr1-/- with Affymetrix exon array analysis and observed in Arr1 -/- up-regulated retinal transcripts including serping1, C4b, C3 and C3a receptor 1 (C3ar1), annexin A1(anxa1), oncostatin M receptor, STAT3, endothelin2, and glial fibrillary acidic protein (GFAP). Top canonical pathways reveal several potential pathways involved in this cone dystrophy phenotype including complement system activation, acute phase response signaling, oncostatin M signaling and JAK3-STAT3 activation. Our data support Arr1 is crucial for regulating an endogenous defense mechanism to ensure survival and normal function of cone photoreceptors.