A ROLE FOR THE INSULIN-INTERLEUKIN (IL)-4 RECEPTOR MOTIF OF THE IL-4 RECEPTOR ALPHA-CHAIN IN REGULATING ACTIVATION OF THE INSULIN-RECEPTOR SUBSTRATE 2 AND SIGNAL TRANSDUCER AND ACTIVATOR OF TRANSCRIPTION 8 PATHWAYS - ANALYSIS BY MUTAGENESIS
Hy. Wang et al., A ROLE FOR THE INSULIN-INTERLEUKIN (IL)-4 RECEPTOR MOTIF OF THE IL-4 RECEPTOR ALPHA-CHAIN IN REGULATING ACTIVATION OF THE INSULIN-RECEPTOR SUBSTRATE 2 AND SIGNAL TRANSDUCER AND ACTIVATOR OF TRANSCRIPTION 8 PATHWAYS - ANALYSIS BY MUTAGENESIS, The Journal of biological chemistry, 273(16), 1998, pp. 9898-9905
The interleukin (IL)-4 receptor alpha-chain (IL-4R alpha) contains a s
equence motif ((488)PLVIAGNPAYRSFSD) termed the insulin IL-4 receptor
motif (I4R motif). Mutation of the central Tyr(497) to Phe blocks the
tyrosine phosphorylation of the insulin receptor substrate 1 (IRS1) an
d diminishes proliferation in response to IL-4. Recent data suggest th
at the I4R motif encodes binding sites for several protein tyrosine bi
nding (PTB) domain-containing proteins such as IRS1 and Shc and potent
ially for the Src homology 2 domain of signal transducer and activator
of transcription 6 (STAT6). To analyze the function of the I4R motif
in regulating IL-4 signaling, we changed conserved residues upstream a
nd downstream of the central Tyr to Ala in the human IL-4R alpha. We a
nalyzed the ability of these constructs to signal the tyrosine phospho
rylation of IRS2 and STAT6, the induction of DNA binding activity, and
CD23 induction in response to human IL-4 (huIL-4) in transfected M12.
4.1 cells. Mutagenesis of residues downstream of Tyr(497), such as Arg
(498) or Phe(500), to Ala had no effect on any of these responses, sug
gesting that the I4R motif may not be important for functional Src hom
ology 2 domain interactions. However, mutagenesis of Pro(488) to Ala (
P488A) greatly diminished the tyrosine phosphorylation of IRS2 and abo
lished tyrosine phosphorylation of STAT6, induction of DNA binding act
ivity, and CD23 induction in response to huIL-4. By contrast, a P488G
mutant signaled these responses to huIL-4. Mutagenesis of hydrophobic
amino acids previously shown to contact the PTB domain of IRS1, Leu(48
9) or Ile(491), to Ala had only minimal effects on responses to huIL-4
. However, changing both Leu(498) and Ile(491) to Ala greatly diminish
ed the tyrosine phosphorylation of IRS2 and abolished STAT6 activation
. Taken together, these results indicate the important role of the I4R
motif in regulating IRS docking and suggest that I4R docking to a PTB
domain-containing protein regulates activation of the STAT6 pathway.