Blood, 1 March 2001, Vol. 97, No. 5, pp. 1343-1351
IMMUNOBIOLOGY
SHIP's C-terminus is essential for its hydrolysis of
PIP3 and inhibition of mast cell degranulation
Jacqueline E. Damen,
Mark
D. Ware,
Janet Kalesnikoff,
Michael R. Hughes, and
Gerald Krystal
From the Terry Fox Laboratory, British Columbia Cancer
Agency, Vancouver, British Columbia, Canada.
The SH2-containing inositol-5'-phosphatase, SHIP, restrains bone
marrow-derived mast cell (BMMC) degranulation, at least in part, by
hydrolyzing phosphatidylinositol (PI)-3-kinase generated PI-3,4,5-P3 (PIP3) to PI-3,4-P2. To
determine which domains within SHIP influence its ability to hydrolyze
PIP3, bone marrow from SHIP
/ mice was
retrovirally infected with various SHIP constructs. Introduction of
wild-type SHIP into SHIP/ BMMCs reverted the Steel
factor (SF)-induced increases in PIP3, calcium entry, and
degranulation to those observed in SHIP+/+ BMMCs. A
5'-phosphatase dead SHIP, however, could not revert the
SHIP/ response, whereas a SHIP mutant in which the 2 NPXY motifs were converted to NPXFs (2NPXF) could partially revert the
SHIP/ response. SF stimulation of BMMCs expressing
the 2NPXF, which could not bind Shc, led to the same level of
mitogen-activated protein kinase (MAPK) phosphorylation as that seen in
BMMCs expressing the other constructs. Surprisingly, C-terminally
truncated forms of SHIP, lacking different amounts of the proline rich
C-terminus, could not revert the SHIP/ response at all.
These results suggest that the C-terminus plays a critical role in
enabling SHIP to hydrolyze PIP3 and inhibit BMMC degranulation.
