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J.R. Dunlevy, E.D. Koppelman, J.B. Kolberg; The Expression of a SH3BP4–Related Protein in Retinal Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2996.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:SH3BP4 is a gene that is encoded for on human chromosome 2q37.1–.2. The SH3BP4 protein contains domains that belong to both the EH (Eps15–Homology)–network family of endocytosis/intracellular sorting proteins as well as a C–terminal death domain. This unique combination of domains is particularly interesting and potentially important in retinal cell biology. This study examines the expression of a newly identified SH3BP4–related gene that is encoded for on human chromosome 7p21.1. Methods:The SH3BP4–related protein, currently named putative binding protein 7a5, was discovered through a human genome BLAST search. The amino acid sequences of SH3BP4 and 7a5 were compared using MacVector software. The expression of 7a5 mRNA was confirmed by RT–PCR using ARPE–19 total RNA followed by subcloning and DNA sequencing. A 7a5 peptide antibody was generated in rabbits and retinal cell and tissue lysates were analyzed by western blot. Results:7a5 encodes for an 852 amino acid protein and has a deduced molecular weight of 96.5 kD. Like SH3BP4, the related 7a5 protein contains consensus sequences and domains that belong to both the EH–network family of endocytosis proteins and the death domain family of apoptosis proteins including 2 N–P–F repeats, a P–X–X–P sequence, 3 Tyr phosphorylation sites and a C–terminal death domain. However, 7a5 is a smaller protein than SH3BP4 and does not contain an N–terminal SH3 domain. The alignment of the deduced amino acid sequence of 7a5 to SH3BP4 shows that there is a 60% amino acid identity and similarity between these two proteins. The homology between these two related proteins increases in the region of the C–terminal death domain to a 75% amino acid identity and similarity. Expression of 7a5 mRNA in ARPE–19 cells was confirmed using RT–PCR and DNA sequencing. Using a newly raised 7a5 peptide antibody, preliminary results indicate that the 7a5 protein is expressed in ARPE–19 and Y79 cells as well as in neural retina and retinal pigment epithelium tissue extracts. Conclusions:A SH3BP4–related protein, called 7a5 was found to be expressed by retinal cells and tissues. This newly identified protein has domains belonging to the death domain family of apoptosis proteins and the endocytosis EH–network family which indicate that this protein is likely to have fundamental significance to retinal cell biology.
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