Vitamin A is the precursor of at least two critical metabolites in vertebrate biology, 11-cis-retinal, the visual chromophore and retinoic acid, a ligand for nuclear receptors. Absorption of dietary vitamin A and its uptake by targeted body tissues depends on specialized binding proteins, transporters, and enzymes. Key components of the involved metabolic machinery are lecithin: retinol acyltransferase (LRAT), an enzyme that catalyzes the formation of retinyl esters. The physiological role of LRAT has attracted scientific and clinical interest because this enzyme is essential for maintaining systemic vitamin A homeostasis and regenerating visual chromophore. LRAT is also attractive targets for the development of a tissue-specific drug delivery system. Yet, progress in understanding the biochemistry of vitamin A uptake and homeostasis is hindered by a shortage of data regarding the molecular basis of these processes. We have a longstanding research interest focused on understanding LRAT's catalytic and physiological action as well as a mechanism that governs cellular retinoid uptake. Through this application, we propose to elucidate the fundamental molecular mechanism of vitamin A processing by LRAT.
In Aim 1, we will delineate the molecular adaptations that discriminate LRAT from related enzymes to confer its vitamin A specificity. We also will identify the LRAT-specific retinoid binding domain and key residues involved in the substrate-protein interaction.
Specific Aim 2 will focus on determining the molecular mechanism for LRAT's acyltransferase activity. By solving and analyzing crystal structures of HRASLS/LRAT chimeric proteins, we will discover the critical molecular adaptations that led to the acquisition of acyltransferase activity. We will define these changes at several levels, including the general topology of the enzyme, adjustments of the phospholipid binding mode, and the mechanism of water exclusion from the enzyme's active site. Finally, in specific Aim 3, we will examine the retinoid specificity of the enzyme. We will analyze the structures of the chimeric enzymes in their retinoid-bound states to obtain detailed information regarding the exact location and organization of the vitamin A binding site. Together, these studies will contribute novel and comprehensive knowledge, filling the gap in our understanding of the vitamin A metabolism and production of the visual chromophore. Dissecting molecular mechanisms underlying retinoid esterification will pave the way for more efficient treatment of human retinal degenerative diseases.

Public Health Relevance

Vitamin A and its metabolites are essential for the proper visual function. Malfunction of the ocular retinoid uptake and homeostasis is clinically manifested by severe attenuation of retinal functions. Rational development of new therapeutic strategies against eye disease requires better understanding of the molecular principles of vitamin A metabolism. Therefore, the long-term objective of our research is to elucidate the molecular basis for action of the key proteins involved in maintaining ocular retinoid homeostasis by a combination of modern biochemical, structural, and functional approaches. These studies will improve understanding of primary causes of human retinal pathologies and could provide concepts for their prevention.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY023948-03
Application #
9096824
Study Section
Biology of the Visual System Study Section (BVS)
Program Officer
Neuhold, Lisa
Project Start
2014-08-01
Project End
2019-06-30
Budget Start
2016-07-01
Budget End
2017-06-30
Support Year
3
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Case Western Reserve University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Chen, Yuanyuan; Chen, Yu; Jastrzebska, Beata et al. (2018) A novel small molecule chaperone of rod opsin and its potential therapy for retinal degeneration. Nat Commun 9:1976
Gao, Songqi; Parmar, Tanu; Palczewska, Grazyna et al. (2018) Protective Effect of a Locked Retinal Chromophore Analog against Light-Induced Retinal Degeneration. Mol Pharmacol 94:1132-1144
Gorelenkova Miller, Olga; Cole, Kyle S; Emerson, Corey C et al. (2017) Novel chloroacetamido compound CWR-J02 is an anti-inflammatory glutaredoxin-1 inhibitor. PLoS One 12:e0187991
Chelstowska, Sylwia; Widjaja-Adhi, Made Airanthi K; Silvaroli, Josie A et al. (2017) Impact of LCA-Associated E14L LRAT Mutation on Protein Stability and Retinoid Homeostasis. Biochemistry 56:4489-4499
Silvaroli, Josie A; Pleshinger, Matthew J; Banerjee, Surajit et al. (2017) Enzyme That Makes You Cry-Crystal Structure of Lachrymatory Factor Synthase from Allium cepa. ACS Chem Biol 12:2296-2304
Arne, Jason M; Widjaja-Adhi, Made Airanthi K; Hughes, Taylor et al. (2017) Allosteric modulation of the substrate specificity of acyl-CoA wax alcohol acyltransferase 2. J Lipid Res 58:719-730
Sundermeier, Thomas R; Sakami, Sanae; Sahu, Bhubanananda et al. (2017) MicroRNA-processing Enzymes Are Essential for Survival and Function of Mature Retinal Pigmented Epithelial Cells in Mice. J Biol Chem 292:3366-3378
Widjaja-Adhi, Made Airanthi K; Palczewski, Grzegorz; Dale, Kali et al. (2017) Transcription factor ISX mediates the cross talk between diet and immunity. Proc Natl Acad Sci U S A 114:11530-11535
Babino, Darwin; Golczak, Marcin; Kiser, Philip D et al. (2016) The Biochemical Basis of Vitamin A3 Production in Arthropod Vision. ACS Chem Biol 11:1049-57
Silvaroli, Josie A; Arne, Jason M; Chelstowska, Sylwia et al. (2016) Ligand Binding Induces Conformational Changes in Human Cellular Retinol-binding Protein 1 (CRBP1) Revealed by Atomic Resolution Crystal Structures. J Biol Chem 291:8528-40

Showing the most recent 10 out of 24 publications