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.
Hinterhuber
Gabriele
G
Department of Dermatology, Division of General Dermatology, University of Vienna, School of Medicine, Vienna, Austria. gabriele.hinterhuber@akh_wien.ac.at
Cauza
Karla
K
Brugger
Karin
K
Dingelmaier-Hovorka
Ruth
R
Horvat
Reinhard
R
Wolff
Klaus
K
Foedinger
Dagmar
D
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