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The peptide product of a 5' leader cistron in the beta 2 adrenergic receptor mRNA inhibits receptor synthesis.

1994; Elsevier BV; Volume: 269; Issue: 6 Linguagem: Inglês

10.1016/s0021-9258(17)41806-0

1083-351X

Anthony L. Parola, Brian K. Kobilka,

Receptor Mechanisms and Signaling

The 5' leader region of mammalian p2 adrenergic receptor messenger RNAs (mRNA) have a short open reading frame (SOW) preceding the receptor cistron.Mutational inactivation of the sORF start codon increased p2 receptor expression and translation 1.9-fold from p2 receptor genes transfected into COS-7 cells.SORI? inactivation also increased receptor synthesis 2.4-fold in a cell-free expression system that synthesizes functional p2 receptor in vitro.Translational initiation at the sORF was demonstrated both in vitro and in transfected COS-7 cells using an epitope-tagged fusion protein.Using the fusion protein as a reporter for initiation at the sORF shows that 5' leader mutations which increase translation of the sORF decrease receptor translation.Mutation analysis of the 5' leader region and peptide coding sequences suggests the peptide itself inhibits p2 receptor expression.Consistent with this hypothesis, a synthetic peptide corresponding to the peptide encoded by the p2 receptor S O W potently inhibits translation in vitro.Our results suggest that a nonoverlapping cistron in the p2 receptor mRNA 5' leader region is translated and the resulting peptide inhibits receptor translation.p2 Adrenergic receptors are low abundance membrane-integrated proteins that mediate the effects of catecholamines at the cell surface.p2 receptor messenger RNA (mRNA) is transcribed from a single intronless gene (1).Receptor transcripts from several mammalian species have a well conserved 5' leader region approximately 220 nucleotides long (1, 2).This leader region harbors a short open reading frame (s0RF)l encoding a 19-amino acid leader peptide of unknown significance.An earlier study showed truncating the p2 receptor transcript 5' leader region (to approximately 40 nucleotides preceding the receptor initiation codon) increased receptor expression and translation (3).Several features of 5' leader regions are known to inhibit translation of the major open reading frame (4), a n d two of these features are found in the pz receptor transcript: 1) a GC-rich region that may form secondary RNA structures or 2) AUG triplets that decrease translation of the major open reading frame.The AUG triplet that serves as the putative site for translational initiation at the sORF is in a poor sequence context for initiation (5).