Our long term goal is to elucidate the mechanisms responsible for the functional polarity and retinal- support functions of the retinal pigment epithelium (RPE). The vast array of support functions the RPE performs for the neural retina require RPE-specific polarity of solute transporters, channels and nutrient receptors and functional tight junctions. The polarity of RPE transporters is frequently opposite to the polarity displayed by the same transporters in other body epithelia. Our central hypothesis is that the organization of RPE polarity and its selective blood-retinal barrier properties is dictated by a tissue-specific configuration of the trafficking machinery in RPE cells and by instructive interactions from choroid endothelial cells. Indeed, we recently reported that RPE cells lack a key clathrin adaptor, AP1B, that sorts basolateral PM proteins in most body epithelia, which explains the reversed apical polarity or non-polarized distribution of several RPE PM proteins (e.g. the coxsackie adenovirus receptor (CAR) and neural adhesion molecule (NCAM)). On the other hand, the mechanisms that regulate the reversed apical polarity of some basolateral PM protein in RPE, e.g. the chloride channel ClC-2 and Na,K-ATPase is not explained by lack of this clathrin adaptor. The research plan of this proposal is focused on understanding the sorting mechanisms and functions of proteins involved in the transport of fluid by RPE, a process of major significance in RPE physiology and retinal pathology, and on characterizing a novel choroid-supported mechanism for the assembly of functional RPE tight junctions.
Specific aim 1 will focus on ClC-2, a key basolateral regulator of cell volume in many epithelia which we recently found, unexpectedly, to be localized to the apical PM and primary cilium of RPE.
Specific aim 2 will focus on NKCC-1 a key Cl- co-transporter in the apical PM of RPE which is expressed basolaterally in other body epithelia and on Bestrophin, a basolateral chloride channel which was recently crystallized and is now therefore amenable for structure-function sorting studies. Finally, specific aim 3 will characterize an exciting new mechanism we have uncovered that regulates the blood-retinal outer barrier through choroid endothelial signals that regulate the maturation of the Bruch basement membrane. We anticipate that the new information and concepts provided by these studies will contribute important insights on the Physiology and Pathology of the Outer Retina that may help generate novel therapeutic strategies for the treatment of diseases of the outer retina.
To perform their key visual function, the rods and cones in the retina depend for support and survival on neighboring cell layers, the retinal pigment epithelium or RPE the choroid vascular layer. This proposal aims to understand in detail how RPE cells organize themselves to provide life support for the rods and cones and how Choroid blood vessels interact with RPE, modulating this process. The information obtained may help develop cures for some blinding diseases, e.g. macular edema and macular degeneration.
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|Benedicto, Ignacio; Lehmann, Guillermo L; Ginsberg, Michael et al. (2017) Concerted regulation of retinal pigment epithelium basement membrane and barrier function by angiocrine factors. Nat Commun 8:15374|
|Perez Bay, Andres E; Schreiner, Ryan; Benedicto, Ignacio et al. (2016) The fast-recycling receptor Megalin defines the apical recycling pathway of epithelial cells. Nat Commun 7:11550|
|Tanos, Barbara E; Perez Bay, Andres E; Salvarezza, Susana et al. (2015) IQGAP1 controls tight junction formation through differential regulation of claudin recruitment. J Cell Sci 128:853-62|
|Song, Minseok; Giza, Joanna; Proenca, Catia C et al. (2015) Slitrk5 Mediates BDNF-Dependent TrkB Receptor Trafficking and Signaling. Dev Cell 33:690-702|
|Bay, Andres E Perez; Schreiner, Ryan; Rodriguez-Boulan, Enrique (2015) Structural and functional analysis of endosomal compartments in epithelial cells. Methods Cell Biol 130:271-88|
|Thuenauer, Roland; Hsu, Ya-Chu; Carvajal-Gonzalez, Jose Maria et al. (2014) Four-dimensional live imaging of apical biosynthetic trafficking reveals a post-Golgi sorting role of apical endosomal intermediates. Proc Natl Acad Sci U S A 111:4127-32|
|Nociari, Marcelo M; Lehmann, Guillermo L; Perez Bay, Andres E et al. (2014) Beta cyclodextrins bind, stabilize, and remove lipofuscin bisretinoids from retinal pigment epithelium. Proc Natl Acad Sci U S A 111:E1402-8|
|Rodriguez-Boulan, Enrique; Macara, Ian G (2014) Organization and execution of the epithelial polarity programme. Nat Rev Mol Cell Biol 15:225-42|
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