Inhibition of ErbB-2 mitogenic and transforming activity by RALT, a mitogen-induced signal transducer which binds to the ErbB-2 kinase domain.
The product of rat gene 33 was identified as an ErbB-2-interacting protein in a two-hybrid screen employing the ErbB-2 juxtamembrane and kinase domains as bait. This interaction was reproduced in vitro with a glutathione S-transferase fusion protein spanning positions 282 to 395 of the 459-residue gene 33 protein. Activation of ErbB-2 catalytic function was required for ErbB-2-gene 33 physical interaction in living cells, whereas ErbB-2 autophosphorylation was dispensable. Expression of gene 33 protein was absent in growth-arrested NIH 3T3 fibroblasts but was induced within 60 to 90 min of serum stimulation or activation of the ErbB-2 kinase and decreased sharply upon entry into S phase. New differentiation factor stimulation of mitogen-deprived mammary epithelial cells also caused accumulation of gene 33 protein, which could be found in a complex with ErbB-2. Overexpression of gene 33 protein in mouse fibroblasts inhibited (i) cell proliferation driven by ErbB-2 but not by serum, (ii) cell transformation induced by ErbB-2 but not by Ras or Src, and (iii) sustained activation of ERK 1 and 2 by ErbB-2 but not by serum. The gene 33 protein may convey inhibitory signals downstream to ErbB-2 by virtue of its association with SH3-containing proteins, including GRB-2, which was found to associate with gene 33 protein in living cells. These data indicate that the gene 33 protein is a feedback inhibitor of ErbB-2 mitogenic function and a suppressor of ErbB-2 oncogenic activity. We propose that the gene 33 protein be renamed with the acronym RALT (receptor-associated late transducer).
Fiorentino
L
L
Laboratories of Immunology, Regina Elena Cancer Institute, 00158 Rome, Italy.
Pertica
C
C
Fiorini
M
M
Talora
C
C
Crescenzi
M
M
Castellani
L
L
Alemà
S
S
Benedetti
P
P
Segatto
O
O
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins; D020134:Catalytic Domain; D002453:Cell Cycle; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008934:Mitogens / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D018909:src Homology Domains
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D008934:Mitogens; D011506:Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; C000629925:Errfi1 protein, rat