A region containing a proline-rich motif targets sG(i2) to the golgi apparatus.
The central function of heterotrimeric GTP-binding proteins (G proteins) is the transduction of extracellular signals, via membrane receptors, leading to the activation of intracellular effectors. In addition to being associated with the plasma membrane, the alpha subunits of some of these proteins have also been localized in intracellular compartments. The mRNA of the G-protein inhibitory alpha subunit 2 (G(alphai2)) encodes two proteins, G(alphai2) and sG(i2), by an alternative splicing mechanism. sG(i2) differs from G(alphai2) in the C-terminal region and localizes in the Golgi in contrast to the plasma membrane localization of G(alphai2). In this paper we show that the sequence specific to sG(i2) can direct the Golgi localization of other G(alphai) subunits, but not of the stimulatory subunit G(alphas) or of a secreted protein. This indicates that, in addition to the sG(i2) C-terminus, sequences located elsewhere in the protein are required to determine the Golgi localization. Inside the sG(i2) C-terminal region we have identified a 14-amino-acid proline-rich motif which specifies the Golgi localization. Finally, we show that the sG(i2) subunit, once activated, leaves the Golgi to be localized in the endoplasmic reticulum.
Picetti
R
R
Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Illkirch Cedex, C. U. de Strasbourg, 67404, France.
Borrelli
E
E
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D006056:Golgi Apparatus / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011392:Proline; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
D011518:Proto-Oncogene Proteins; D011392:Proline; C498015:GNAI2 protein, human; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins