Focal adhesion kinase signaling promotes phagocytosis of integrin-bound photoreceptors. 2003

Silvia C Finnemann
Dyson Vision Research Institute, Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY 10021, USA. sfinne@med.cornell.edu

Daily alphavbeta5 integrin-dependent phagocytosis of spent photoreceptor outer segment fragments by the retinal pigment epithelium (RPE) is critical for retinal function. This study identifies a key role for focal adhesion kinase (FAK) in RPE phagocytosis. Particle binding increases FAK complex formation with alphavbeta5 receptors at the apical, phagocytic RPE surface and activates FAK. Subsequent particle engulfment coincides with dissociation of activated FAK from alphavbeta5. Mutant FAK retaining focal adhesion targeting but lacking kinase activity interferes with recruitment of full-length FAK to alphavbeta5 and abrogates FAK activation in response to RPE phagocytic challenge. Such inhibition of FAK signaling has no effect on alphavbeta5-dependent binding of particles but blocks their engulfment. Conversely, FAK re-expression promotes particle engulfment by FAK null fibroblasts. Selective ligation of alphavbeta5 receptors at the apical RPE surface is sufficient to phosphorylate and mobilize FAK. Furthermore, FAK phagocytic signaling is independent of the internalization receptor MerTK. In contrast, inhibition of FAK signaling diminishes MerTK phosphorylation. These results demonstrate that FAK provides an essential link between binding and engulfment mechanisms of integrin-mediated phagocytosis.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008164 Luminescent Proteins Proteins which are involved in the phenomenon of light emission in living systems. Included are the "enzymatic" and "non-enzymatic" types of system with or without the presence of oxygen or co-factors. Bioluminescent Protein,Bioluminescent Proteins,Luminescent Protein,Photoprotein,Photoproteins,Protein, Bioluminescent,Protein, Luminescent,Proteins, Bioluminescent,Proteins, Luminescent
D010587 Phagocytosis The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES). Phagocytoses
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D010786 Photoreceptor Cells Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade. Ciliary Photoreceptor Cells,Ciliary Photoreceptors,Rhabdomeric Photoreceptor Cells,Rhabdomeric Photoreceptors,Cell, Ciliary Photoreceptor,Cell, Photoreceptor,Cell, Rhabdomeric Photoreceptor,Cells, Ciliary Photoreceptor,Cells, Photoreceptor,Cells, Rhabdomeric Photoreceptor,Ciliary Photoreceptor,Ciliary Photoreceptor Cell,Photoreceptor Cell,Photoreceptor Cell, Ciliary,Photoreceptor Cell, Rhabdomeric,Photoreceptor Cells, Ciliary,Photoreceptor Cells, Rhabdomeric,Photoreceptor, Ciliary,Photoreceptor, Rhabdomeric,Photoreceptors, Ciliary,Photoreceptors, Rhabdomeric,Rhabdomeric Photoreceptor,Rhabdomeric Photoreceptor Cell
D010857 Pigment Epithelium of Eye The layer of pigment-containing epithelial cells in the RETINA; the CILIARY BODY; and the IRIS in the eye. Eye Pigment Epithelium
D011505 Protein-Tyrosine Kinases Protein kinases that catalyze the PHOSPHORYLATION of TYROSINE residues in proteins with ATP or other nucleotides as phosphate donors. Tyrosine Protein Kinase,Tyrosine-Specific Protein Kinase,Protein-Tyrosine Kinase,Tyrosine Kinase,Tyrosine Protein Kinases,Tyrosine-Specific Protein Kinases,Tyrosylprotein Kinase,Kinase, Protein-Tyrosine,Kinase, Tyrosine,Kinase, Tyrosine Protein,Kinase, Tyrosine-Specific Protein,Kinase, Tyrosylprotein,Kinases, Protein-Tyrosine,Kinases, Tyrosine Protein,Kinases, Tyrosine-Specific Protein,Protein Kinase, Tyrosine-Specific,Protein Kinases, Tyrosine,Protein Kinases, Tyrosine-Specific,Protein Tyrosine Kinase,Protein Tyrosine Kinases,Tyrosine Specific Protein Kinase,Tyrosine Specific Protein Kinases
D011518 Proto-Oncogene Proteins Products of proto-oncogenes. Normally they do not have oncogenic or transforming properties, but are involved in the regulation or differentiation of cell growth. They often have protein kinase activity. Cellular Proto-Oncogene Proteins,c-onc Proteins,Proto Oncogene Proteins, Cellular,Proto-Oncogene Products, Cellular,Cellular Proto Oncogene Proteins,Cellular Proto-Oncogene Products,Proto Oncogene Products, Cellular,Proto Oncogene Proteins,Proto-Oncogene Proteins, Cellular,c onc Proteins
D011922 Rats, Mutant Strains Rats bearing mutant genes which are phenotypically expressed in the animals. Mutant Strains Rat,Mutant Strains Rats,Rat, Mutant Strains,Strains Rat, Mutant,Strains Rats, Mutant
D002448 Cell Adhesion Adherence of cells to surfaces or to other cells. Adhesion, Cell,Adhesions, Cell,Cell Adhesions

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