The Journal of Neuroscience, November 1, 1999, 19(21):9538-9549
Regulation of Learning by EphA Receptors: a Protein Targeting
Study
R.
Gerlai1,
N.
Shinsky1,
A.
Shih1,
P.
Williams2,
J.
Winer2,
M.
Armanini1,
B.
Cairns3,
J.
Winslow1,
W.-Q.
Gao1, and
H. S.
Phillips1
Genentech, Inc., Departments of 1 Neuroscience,
2 Research BioAssay, and 3 Pathology, South San
Francisco, California 94080
EphA family receptor tyrosine kinases and their ephrin-A ligands
are involved in patterning axonal connections during brain development,
but until now a role for these molecules in the mature brain had not
been elucidated. Here, we show that both the EphA5 receptor and its
ephrin-A ligands (2 and 5) are expressed in the adult mouse
hippocampus, and the EphA5 protein is present in a phosphorylated form.
Because there are no pharmacological agents available for EphA
receptors, we designed recombinant immunoadhesins that specifically
bind to the receptor binding site of the ephrin-A ligand (antagonist)
or the ligand binding site of the EphA receptor (agonist) and thus
target EphA function. We demonstrate that intrahippocampal infusion of
an EphA antagonist immunoadhesin leads to impaired performance in two
behavioral paradigms, T-maze spontaneous alternation and
context-dependent fear conditioning, sensitive to hippocampal function,
whereas activation of EphA by infusion of an agonist immunoadhesin
results in enhanced performance on these tasks. Because the two
behavioral tasks have different motivational, perceptual, and motor
requirements, we infer the changes were not caused by these
performance factors but rather to cognitive alterations. We also find
bidirectional changes in gene expression and in electrophysiological
measures of synaptic efficacy that correlate with the behavioral
results. Thus, EphA receptors and their ligands are implicated as
mediators of plasticity in the adult mammalian brain.
Key words:
EphA tyrosine kinase receptor; immunoadhesin; learning; mouse; hippocampus; inbred strain; LTP
Copyright © 1999 Society for Neuroscience 0270-6474/99/19219538-12$05.00/0