PubMed Journals: J Biol Chem
Source: PMID: 9685404
⇦ ⇨ J Biol Chem. 1998 Aug 7;273(32):20487-93.
Tyrosine 474 of ZAP-70 is required for association
with the Shc adaptor and for T-cell antigen
receptor-dependent gene activation.
Pacini S(1), Ulivieri C, Di Somma MM, Isacchi
A, Lanfrancone L, Pelicci PG, Telford JL,
(1) Department of Evolutionary Biology,
University of Siena, Via Mattioli 4, 53100
The protein tyrosine kinase ZAP-70 plays
a central role in T-cell activation. Following
receptor engagement, ZAP-70 is recruited
to the phosphorylated subunits of the T-cell
antigen receptor (TCR). This event results
in ZAP-70 activation and in association
of ZAP-70 with a number of signaling proteins.
Among these is the Shc adaptor, which couples
the activated TCR to Ras. Shc interaction
with ZAP-70 is mediated by the Shc PTB domain.
The inhibitory effect of a Shc mutant containing
the isolated PTB domain suggests that Shc
interaction with ZAP-70 might be required
for TCR signaling. Here, we show that a
point mutation (Phe474) of the putative
Shc binding site on ZAP-70, spanning tyrosine
474, prevented ZAP-70 interaction with Shc
and the subsequent binding of Shc to phospho-zeta.
Neither ZAP-70 catalytic activity nor the
pattern of protein phosphorylation induced
by TCR triggering was affected by this mutation.
However expression of the Phe474 ZAP-70
mutant resulted in impaired TCR-dependent
gene activation. ZAP-70 could effectively
phosphorylate Shc in vitro. Only the CH
domain, which contains the two Grb2 binding
sites on Shc, was phosphorylated by ZAP-70.
Both Grb2 binding sites were excellent substrates
for ZAP-70. The data show that Tyr474 on
ZAP-70 is required for TCR signaling and
suggest that Shc association with ZAP-70
and the resulting phosphorylation of Shc
might be an obligatory step in linking the
activated TCR to the Ras pathway.
PMID: 9685404 [Indexed for MEDLINE]