PREDOMINANT EXPRESSION OF TYPE-II VASOACTIVE-INTESTINAL-PEPTIDE RECEPTORS BY HUMAN T-LYMPHOBLASTOMA CELLS - TRANSDUCTION OF BOTH CA2-AMP SIGNALS( AND CYCLIC)
Mh. Xia et al., PREDOMINANT EXPRESSION OF TYPE-II VASOACTIVE-INTESTINAL-PEPTIDE RECEPTORS BY HUMAN T-LYMPHOBLASTOMA CELLS - TRANSDUCTION OF BOTH CA2-AMP SIGNALS( AND CYCLIC), Journal of clinical immunology, 16(1), 1996, pp. 21-30
An immunoregulatory role for vasoactive intestinal peptide (VIP) is su
ggested by the high concentrations in subsets of neurons supplying lym
phoid organs and by the capacity of VIP to affect T lymphocyte functio
ns. The Tsup-1 line of human T lymphoblastoma cells expresses both typ
e I and type II G protein-coupled VTP receptors (Rs), as shown by dete
ction of the encoding mRNAs with reverse transcription-polymerase chai
n reaction analyses. Northern blot quantification of the relative amou
nts of mRNA encoding the two VIPRs in Tsup-1 cells indicated that type
II predominates over type I, as it does in human blood CD4(+) T cells
. Tsup-1 cells bound I-125-VIP to 8.95 X 10(4) high-affinity sites/cel
l (K-d = 6.0 nM) and 7.45 x 10(5) low-affinity sites/cell (K-d = 210 n
M). VIP increased [cAMP](i) in Tsup-1 cells (EC(50) = 14.4 nM) and sti
mulated a rapid and transient increase in [Ca2+](i) (EC(50) = 30 nM).
Functional coupling of G proteins to type II VIPRs was suggested by th
e change in binding of I-125-V1P to Tsup-1 cell membranes from two sit
es with K-d values of 3.8 and 109 nM to one site of K-d 30 nM by GTP-g
amma-S and the suppression by pertussis toxin of increases in [Ca2+](i
) evoked by VIP. The VIP antagonists, VIP4-28, and (4-Cl-D-Phe(6)-Leu(
17)) VIP, inhibited I-125-VIP binding by type II VIPRs, as well as VIP
-elicited increases in [Ca2+](i) and [cAMP](i). Type II VIPRs thus are
the major transducers of VIP signals to a subset of human T cells.