Phosphatidylinositol 4,5-bisphosphate (PIP2) activates KATP and other inward rectifier (Kir) channels. To determine residues important for PIP2 regulation, we have systematically mutated each positive charge in the COOH terminus of Kir6.2 to alanine. The effects of these mutations on channel function were examined using 86Rb efflux assays on intact cells and inside-out patch-clamp methods. Both methods identify essentially the same basic residues in two narrow regions (176–222 and 301–314) in the COOH terminus that are important for the maintenance of channel function and interaction with PIP2. Only one residue (R201A) simultaneously affected ATP and PIP2 sensitivity, which is consistent with the notion that these ligands, while functionally competitive, are unlikely to bind to identical sites. Strikingly, none of 13 basic residues in the terminal portion (residues 315–390) of the COOH terminus affected channel function when neutralized. The data help to define the structural requirements for PIP2 sensitivity of KATP channels. Moreover, the regions and residues defined in this study parallel those uncovered in recent studies of PIP2 sensitivity in other inward rectifier channels, indicating a common structural basis for PIP2 regulation.

Purpose We investigate whether ocular and person-based characteristics are associated with dark adaptation (DA) measured using the AdaptRx™ device (Apeliotus Technologies, Atlanta, GA). Design Cross-sectional, single-center, observational study. Participants 116 participants >50 years with a range in age-related macular degeneration (AMD) severity. Methods Participants underwent best-corrected visual acuity (BCVA) testing, ophthalmoscopic examination and multimodal imaging. Presence of reticular pseudodrusen (RPD) was assessed by masked grading of fundus images and confirmed with OCT. Eyes were also graded for AMD features (drusen, pigmentary changes, late AMD) to generate a person-based AMD severity groups. One eye was designated the study eye for DA testing using the AdaptRx™ device. Nonparametric statistical testing was performed on all comparisons. Main Outcome Measure The primary outcome of this study was the rod-intercept time (RIT) which is defined as the time for a participant's visual sensitivity to recover to a stimulus intensity of 5 × 10−3 cd/m2 (a decrease of 3 log units), or until a maximum test duration of 40 minutes was reached. Results A total of 116 study eyes in 116 participants (mean age=75.4±9.4 years, 58% female) were analyzed. Increased RIT was significantly associated with increasing age (r=0.34, p=0.0002), decreasing BCVA (r=−0.54, p<0.0001), pseudophakia (p=0.03), decreasing subfoveal choroidal thickness (r=−0.27, p=0.003). Study eyes with RPD (15/116, 13%) had a significantly greater mean RIT compared to eyes without RPD in any AMD severity group (p<0.02 for all comparisons) with 80% reaching the DA test ceiling. Conclusion Impairments in DA increase with age, worse visual acuity, presence of RPD, AMD severity and decreased subfoveal choroidal thickness. Analysis of covariance found the multivariable model that best fit our data included age, AMD group, and presence of RPD (R2=0.56) with the presence of RPD conferring the largest parameter estimate.

Objective-To describe the natural history of eyes with drusenoid pigment epithelial detachments (DPED) associated with age-related macular degeneration (AMD). Design-Multi-center clinic-based prospective cohort study.Participants-Among 4757 participants enrolled in the Age-Related Eye Disease Study (AREDS), 255 were identified as having DPED in at least one eye and having 5 or more years of follow-up after the initial detection of the DPED.Methods-Baseline and annual fundus photographs were evaluated for the evolution of the fundus features and the development of advanced AMD in the forms of central geographic atrophy (CGA) or neovascular (NV) AMD. Kaplan-Meier analyses of progression to advanced AMD and of moderate vision loss (≥15 letters compared with baseline) were performed.Main Outcome Measures-Rate of progression to advanced AMD and change in visual acuity from baseline (in terms of mean letters lost and proportion losing ≥15 letters).Results-A total of 311 eyes (from 255 participants) with DPED were followed for a median follow-up time of 8 years subsequent to the initial detection of a DPED. Of the 282 eyes that did not have advanced AMD at baseline, advanced AMD developed within 5 years in 119 eyes (42%) (19% progressing to CGA and 23% to NV-AMD). In the remaining eyes that did not develop advanced AMD (n = 163), progressive fundus changes, typified by the development of calcified drusen and pigmentary changes, were detected. Visual decline was prominent among study eyes, with Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptOphthalmology. Author manuscript; available in PMC 2011 March 1. Published in final edited form as:Ophthalmology. Conclusion-The natural history of eyes containing DPED is characterized by a high rate of progression to both CGA and NV-AMD. Among eyes not progressing advanced AMD, progressive development of pigmentary changes and calcified drusen were observed. Decline of visual acuity is a common outcome, with or without progression to advanced forms of AMD.