Regulation of sorting and post-Golgi trafficking of rhodopsin by its C-terminal sequence QVS(A)PA.
Several mutations that cause severe forms of the human disease autosomal dominant retinitis pigmentosa cluster in the C-terminal region of rhodopsin. Recent studies have implicated the C-terminal domain of rhodopsin in its trafficking on specialized post-Golgi membranes to the rod outer segment of the photoreceptor cell. Here we used synthetic peptides as competitive inhibitors of rhodopsin trafficking in the frog retinal cell-free system to delineate the potential regulatory sequence within the C terminus of rhodopsin and model the effects of severe retinitis pigmentosa alleles on rhodopsin sorting. The rhodopsin C-terminal sequence QVS(A)PA is highly conserved among different species. Peptides that correspond to the C terminus of bovine (amino acids 324-348) and frog (amino acids 330-354) rhodopsin inhibited post-Golgi trafficking by 50% and 60%, respectively, and arrested newly synthesized rhodopsin in the trans-Golgi network. Peptides corresponding to the cytoplasmic loops of rhodopsin and other control peptides had no effect. When three naturally occurring mutations: Q344ter (lacking the last five amino acids QVAPA), V345M, and P347S were introduced into the frog C-terminal peptide, the inhibitory activity of the peptides was no longer detectable. These observations suggest that the amino acids QVS(A)PA comprise a signal that is recognized by specific factors in the trans-Golgi network. A lack of recognition of this sequence, because of mutations in the last five amino acids causing autosomal dominant retinitis pigmentosa, most likely results in abnormal post-Golgi membrane formation and in an aberrant subcellular localization of rhodopsin.
Department of Ophthalmology, University of Michigan, Ann Arbor, MI 48105, USA. dereticd@umich.edu
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Deretic
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Schmerl
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Hargrave
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Arendt
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JH
McDowell
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002474:Cell-Free System; D006056:Golgi Apparatus / Q000378:metabolism*; D008969:Molecular Sequence Data; D011898:Ranidae; D012160:Retina / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry / Q000378:metabolism*
D012243:Rhodopsin