Recoverin Regulates Light-dependent Phosphodiesterase Activity in Retinal Rods

The Ca2+-binding protein recoverin may regulate visual transduction in retinal rods and cones, but its functional role and mechanism of action remain controversial. We compared the photoresponses of rods from control mice and from mice in which the recoverin gene was knocked out. Our analysis indicates that Ca2+-recoverin prolongs the dark-adapted flash response and increases the rod's sensitivity to dim steady light. Knockout rods had faster Ca2+ dynamics, indicating that recoverin is a significant Ca2+ buffer in the outer segment, but incorporation of exogenous buffer did not restore wild-type behavior. We infer that Ca2+-recoverin potentiates light-triggered phosphodiesterase activity, probably by effectively prolonging the catalytic activity of photoexcited rhodopsin

Clinical disorders affecting mesopic vision

Vision in the mesopic range is affected by a number of inherited and acquired clinical disorders. We review these conditions and summarize the historical background, describing the clinical characteristics alongside the genetic basis and molecular biological mechanisms giving rise to rod and cone dysfunction relevant to twilight vision. The current diagnostic gold standards for each disease are discussed and curative and symptomatic treatment strategies are summarized

Expression of GCAP 1 and GCAP2 in the retinal degeneration (rd) mutant chicken retina

AbstractWe cloned the guanylate cyclase activating proteins, GCAP1 and GCAP2, from chicken retina and examined their expression in normal and predegenerate rd/rd chicken retina. Northern analyses show that the amounts of the single transcripts encoding GCAPI and GCAP2 are reduced to about 70% of normal levels in rdlrd retina. Western analyses reveal that GCAP2 levels appear normal in this retina, while GCAPI levels are reduced by more than 90%. The specific downregulation of GCAPI in rd/rd retina is consistent with a model for this disease in which activation of guanylate cyclase in the photoreceptors is abnormal, resulting in low levels of cGMP and an absence of phototransduction

Diagnostic yield of commercial immunodots to diagnose paraneoplastic neurologic syndromes

OBJECTIVE: To investigate the diagnostic yield of commercial immunodots to detect onconeural antibodies associated with paraneoplastic neurologic syndromes (PNSs), we analyzed the proportion of confirmed positive results using alternative techniques. METHODS: Sera (n = 5,300) of patients with suspected PNS were tested by PNS+2 blot (Ravo Diagnostika; January 2016-May 2017) or EUROLINE PNS 12 Ag (Euroimmun; July 2017-November 2018). Positive samples were further explored by in-house indirect immunofluorescence and a third in-house technique (Western blot or cell-based assay) using recombinant protein. Those found negative by these 2 techniques were considered as nonconfirmed. We analyzed the relationship between band intensity and final confirmation. Clinical data were collected for all confirmed results and nonconfirmed EUROLINE immunodots. RESULTS: PNS+2 blot was positive in 128/1,658 (7.7%) sera and confirmed in 47/128 (36.7%). EUROLINE was positive in 186/3,626 (5.1%) and confirmed in 56/186 (30.1%). Confirmation was highly variable among the antibodies tested, from 7.2% (PNS+2 blot) and 5.8% (EUROLINE) for anti-Yo to 88.2% (PNS+2 blot) and 65.0% (EUROLINE) for anti-Hu. None of the 27 weak positive sera by EUROLINE was confirmed. Band intensity in confirmed cases was variable among the antibodies from strong positive for all anti-Yo (n = 3) and anti-Hu (n = 11) to positive (n = 19) or strong positive (n = 9) for anti-SOX1. Among patients with a nonconfirmed EUROLINE result and available clinical information, all had an alternative diagnosis, and only 6.7% had cancer. CONCLUSIONS: Immunodots may be useful for PNS screening, but a threshold should be established for each antibody, and clinical information and confirmation by other techniques are essential. CLASSIFICATION OF EVIDENCE: The study provides Class IV evidence that immunodot assays for onconeural antibodies accurately identify patients with paraneoplastic neurologic syndromes

Regulation of guanylyl cyclase by a cGMP-binding protein during chemotaxis in Dictyostelium discoideum

Chemoattractants transiently activate guanylyl cyclase in Dictyostelium discoideum cells. Mutant analysis demonstrates that the produced cGMP plays an essential role in chemotactic signal transduction, controlling the actomyosin-dependent motive force. Guanylyl cyclase activity is associated with the particulate fraction of a cell homogenate. The addition of the cytosol stimulates guanylyl cyclase activity, whereas the cytosol plus ATP/Mg2+ inhibits enzyme activity, We have analyzed the regulation of guanylyl cyclase in chemotactic mutants and present evidence that a cGMP-binding protein mediates both stimulation and ATP-dependent inhibition of guanylyl cyclase. Upon chromatography of cytosolic proteins, cGMP binding activity co-elutes with both guanylyl cyclase-stimulating and ATP-dependent-inhibiting activities. In addition, ATP-dependent inhibition of guanylyl cyclase activity is enhanced by the cGMP analogue 8-Br-cGMP, suggesting that a cGMP-binding protein regulates guanylyl cyclase activity, Mutant KI-4 has an aberrant cGMP binding activity with very low K-d and shows a very small chemoattractant-mediated cGMP response; the cytosol from this mutant does not stimulate guanylyl cyclase, In contrast to KI-4, the aberrant cGMP binding activity of mutant KI-7 has a very high K-d and chemoattractants induce a prolonged cGMP response. The cytosol of this mutant stimulates guanylyl cyclase activity, but ATP does not inhibit the enzyme. Thus, two previously isolated chemotactic mutants are defective in the activation and inhibition of guanylyl cyclase, respectively. The positive and negative regulation of guanylyl cyclase by its product cGMP may well explain how cells process the temporospatial information of chemotactic signals, which is necessary for sensing the direction of the chemoattractant

DGKA (diacylglycerol kinase, alpha 80kDa)

Review on DGKA, with data on DNA/RNA, on the protein encoded and where the gene is implicated

Sudden acquired retinal degeneration syndrome (SARDS) â a review and proposed strategies toward a better understanding of pathogenesis, early diagnosis, and therapy

Sudden acquired retinal degeneration syndrome (SARDS) is one of the leading causes of currently incurable canine vision loss diagnosed by veterinary ophthalmologists. The disease is characterized by acute onset of blindness due to loss of photoreceptor function, extinguished electroretinogram with an initially normal appearing ocular fundus, and mydriatic pupils which are slowly responsive to bright white light, unresponsive to red, but responsive to blue light stimulation. In addition to blindness, the majority of affected dogs also show systemic abnormalities suggestive of hyperadrenocorticism, such as polyphagia with resulting obesity, polyuria, polydipsia, and a subclinical hepatopathy. The pathogenesis of SARDS is unknown, but neuroendocrine and autoimmune mechanisms have been suggested. Therapies that target these disease pathways have been proposed to reverse or prevent further vision loss in SARDSâ affected dogs, but these treatments are controversial. In November 2014, the American College of Veterinary Ophthalmologists' Vision for Animals Foundation organized and funded a Think Tank to review the current knowledge and recently proposed ideas about disease mechanisms and treatment of SARDS. These panel discussions resulted in recommendations for future research strategies toward a better understanding of pathogenesis, early diagnosis, and potential therapy for this condition.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122446/1/vop12291.pd

Structural and functional protein network analyses predict novel signaling functions for rhodopsin

Proteomic analyses, literature mining, and structural data were combined to generate an extensive signaling network linked to the visual G protein-coupled receptor rhodopsin. Network analysis suggests novel signaling routes to cytoskeleton dynamics and vesicular trafficking