RPE65 of retinal pigment epithelium, a putative receptor molecule for plasma retinol-binding protein, is expressed in human keratinocytes.
Retinoids are important modulators for cell growth and differentiation of normal skin. In plasma, retinol is transported coupled to plasma retinol-binding protein. In this study, we investigated gene and protein expression of RPE65, a putative receptor for plasma retinol-binding protein in human epidermal keratinocytes. We performed real-time PCR analysis to evaluate expression of RPE65 mRNA in proliferating and differentiating keratinocytes. Immunoblotting with anti-RPE65 antibody shows distinct reactivity to a 61-kDa protein. Indirect immunofluorescence on normal human epidermis reveals cell surface labeling of keratinocytes. Laser scan microscopy exhibits colocalization of plasma retinol-binding protein and RPE65 on cultured keratinocytes. Internalization experiments with [3H]retinoic acid-retinol-binding protein complex in the presence and absence of excess of retinol-binding protein indicates receptor-dependent uptake of retinoids. We further show isolation of RPE65 protein by affinity chromatography from lysates of keratinocytes using a retinol-binding protein-matrix gel column. In summary, we demonstrate mRNA and protein expression of RPE65 in epidermal keratinocytes. Colocalization of plasma retinol-binding protein with RPE65 and affinity binding suggest a direct interaction of RPE65 with plasma retinol-binding protein in cultured human keratinocytes that might be involved in retinoid uptake of keratinocytes.
Department of Dermatology, Division of General Dermatology, University of Vienna, School of Medicine, Vienna, Austria. gabriele.hinterhuber@akh_wien.ac.at
Gabriele
G
Hinterhuber
Karla
K
Cauza
Karin
K
Brugger
Ruth
R
Dingelmaier-Hovorka
Reinhard
R
Horvat
Klaus
K
Wolff
Dagmar
D
Foedinger
D000328:Adult; D002352:Carrier Proteins; D002478:Cells, Cultured; D000078404:Epidermal Cells; D005136:Eye Proteins; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000502:physiology*; D007641:Keratolytic Agents / Q000493:pharmacokinetics; D010857:Pigment Epithelium of Eye / Q000378:metabolism; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D054839:Retinol-Binding Proteins, Plasma; D014212:Tretinoin / Q000493:pharmacokinetics; D014316:Tritium; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase
D002352:Carrier Proteins; D005136:Eye Proteins; D007641:Keratolytic Agents; D011506:Proteins; D012333:RNA, Messenger; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma; D014212:Tretinoin; D014316:Tritium; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase