Jg. Altin et al., MOLECULAR ASSOCIATIONS INVOLVING CD16, CD45 AND ZETA-CHAIN AND GAMMA-CHAIN ON HUMAN NATURAL-KILLER-CELLS, Immunology and cell biology, 72(1), 1994, pp. 87-96
zeta (CD3-zeta) and gamma (Fc epsilon RI gamma) chains associate with
CD16, the low affinity receptor for IgG (Fc gamma RIII) on human NK ce
lls and are essential for the cell surface expression of CD16 and for
CD16-mediated effector functions. This study has investigated whether,
on NK cells, molecules other than CD16 associate with zeta and gamma
chains, as a method of identifying other NK cell surface molecules imp
ortant in NK cell function. Cell surface biotinylated NK cells were ly
sed in digitonin, and the lysates immunoprecipitated with mAb to CD16,
zeta and gamma, and the immunoprecipitates analysed by SDS-PAGE. CD 1
6 mAb co-precipitated zeta and gamma chains (16 and 12kD, respectively
) and in addition molecules of 24, 32-35, 100, 150 and 180-200 kD. Als
o, zeta mAb co-precipitated gamma chain, and molecules of 24-26, 32-35
, 48, 50-66, 100, 150 and 180-200 kD; and gamma co-precipitated zeta c
hain, and molecules of 24-26, 29, 32-35, 37, 45, 49, 50-66 and 100 kD.
While significant amounts of zeta and gamma were co-precipitated with
CD 16, 10 to 12-fold more zeta and gamma were immunoprecipitated with
their respective mAb. Furthermore, depletion of CD16 from the lysate
resulted in only a partial (10-12%) depletion of zeta and gamma, indic
ating that only a relatively small proportion (10-12%) of these molecu
les are associated with CD16. Interestingly, substantial amounts of mo
lecules with electrophoretic mobility similar to CD16 (50-66 kD) were
co-precipitated with zeta and gamma chain mAb from lysates depleted of
CD16. In contrast to NK cells where zeta associated with a number of
different molecules, the majority of zeta in T cells was found to be a
ssociated only with the TCR : CD3 complex, NK cells showed a strong as
sociation between CD45, CD 16 and a 33 kD molecule and often a strong
association of zeta with CD16, CD45 and an unidentified molecule of si
milar to 150 kD. Our results show first, that CD16, zeta and gamma eac
h can be efficiently labelled by cell surface biotinylation, and secon
d, that CD16, zeta and gamma each can form a complex with each other,
and with a number of additional molecules including a 33 kD molecule a
nd CD45 potentially important in NK cell function.