function. In addition, reconstitution of functional 
immunoglobulin antigen receptors in T cells offers 
a general solution to the difficult problem of major 
histocompatibility complex (MHC) restriction in 
transfer of cellular immunity. T cells that utilize im- 
munoglobulin receptors would have the potential 
for recognizing any antigen that antibodies recog- 
nize in an MHC-independent fashion. 
Dr. Nussenzweig is also Assistant Professor and 
Head of Laboratory at the Rockefeller University. 
Articles 
Costa, T.E.F., Franke, R.R., Sanchez, M., Misulo- 
vin, Z., and Nussenzweig, M.C. 1992. Func- 
tional reconstitution of an immunoglobulin anti- 
gen receptor in T cells. / Exp Med 175: 
1669-1676. 
Costa, T.E.F., Suh, H., and Nussenzweig, M.C. 
1992. Chromosomal position of rearranging gene 
segments influences allelic exclusion in trans- 
genic mice. Proc Natl Acad Sci USA 89:2205- 
2208. 
NEUROTRANSMITTER RECEPTOR-MEDIATED RESPONSES IN LYMPHOCYTES 
Donald G. Payan, M.D., Assistant Investigator 
Dr. Payan and his colleagues have been studying 
neurotransmitter receptor modulation of lympho- 
cyte surface molecules that regulate cell growth, 
differentiation, and cell-cell interactions. In addi- 
tion, their research is focused on the biochemical 
characterization of the protease inhibitor domains 
of the molecule agrin. Agrin is a glycoprotein ex- 
pressed in the brain and spinal cord during develop- 
ment and regenerative processes. It is also known to 
regulate the localization of acetylcholine receptors 
(AChRs) at the neuromuscular junction. 
Substance P Receptor (SPR) Signal 
Transduction Mechanisms 
A number of recent studies have shown that cer- 
tain peptide receptors, when occupied by ligand, 
may alter their G protein subclass association ac- 
cording to the state of differentiation of the cell, 
resulting in diverse cellular responses. Given the 
wide spectrum of activities associated with SP (va- 
sodilation, mitogenicity of cultured cells, neuro- 
transmission, and change in the trophic and toxic 
cellular responses to amyloid /3 protein) , Dr. Payan 
and his colleagues have focused their attention on 
the second messenger pathways that are activated 
following SPR stimulation. 
The rat SPR cDNA was subcloned into the mam- 
malian expression vector pRC/RSV and transfected 
into a number of cell lines. The group has isolated 
stable transfectants expressing the receptor and has 
demonstrated specific receptor message and '^'l-SP 
binding in SPR-transfected cells but not in untrans- 
fected cells or those transfected by vector alone. 
The functional responses of the stable transfec- 
tants expressing the SPR were first examined by 
measuring SP-induced alterations in intracellular 
Ca^"^ ([Ca^^Ji), using the fluorescent indicator dye 
fura-2. Stimulation with SP transiently increased 
[Ca^^]j in SPR-positive cells in a dose-dependent 
manner, with an EC50 ~ 5 X 1 0"'° M, a value similar 
to the derived from '^^I-SP binding. To examine 
further the possibility that the SPR might also be 
coupled to an additional signaling pathway, intra- 
cellular cAMP levels following SP stimulation were 
quantified. The level of cAMP in SPR-positive cells 
was significantly increased following stimulation by 
SP and was maximal at 5-10 min. The effect of SP 
was dose-dependent, with an EC50 ~ 5 X 10"'° M, a 
value similar to that derived from the [Ca^^jj mobili- 
zation studies. Dr. Payan's group has now been able 
to demonstrate, using forskolin and ionomycin, that 
in desensitization studies, the SPR signals these cells 
simultaneously and independently via the phospha- 
tidylinositol (PI) -coupled and the cAMP-coupled 
pathways, and that the degree to which each path- 
way contributes to the overall SP-mediated response 
is determined by the relative abundance of different 
G proteins. 
To examine whether SP stimulation results in the 
activation of downstream transcriptional regulatory 
factors, the group has transfected KNRK-SPR cells 
with plasmids containing the AP- 1 and CRE (cAMP 
response element) enhancer elements coupled to 
the chloramphenicol acetyltransferase (CAT) re- 
porter gene. Stimulation with SP over a concentra- 
tion range of 1-1,000 nM results in a significant 
increase in CAT activity in both AP-l-CAT- and 
CRE-CAT-transfected KNRK-SPR cells. Northern 
and Western blot analyses demonstrate that the 
mechanism by which SP stimulates AP I enhancer 
IMMUNOLOGY 351 
