Journal of Neuroscience, Vol 14, 2624-2635, Copyright © 1994 by Society for Neuroscience
KT5926 selectively inhibits nerve growth factor-dependent neurite elongation
KK Teng and LA Greene
Department of Pathology and Center for Neurobiology and Behavior, Columbia University, College of Physicians and Surgeons, New York, New York 10032.
We have examined the effects of the protein kinase inhibitor KT5926 on
NGF-promoted responses in PC12 and PC12-C41 cells (a subclone of the
parental cell line). Our findings reveal that this compound specifically
and reversibly prevents the NGF-induced outgrowth and regeneration of
neurites. In addition, neurites of NGF-pretreated cells cease further
elongation upon exposure to KT5926. However, preexisting neurite networks
in the cultures remain intact in the presence of the drug. The inhibition
of neuritic growth appears to occur at least in part at the level of growth
cones since KT5926 also causes these structures to collapse and inhibits
NGF-promoted reactivation of NGF- deprived growth cones. Although KT5926 is
an analogue of K-252a, which blocks all responses to NGF, it does not
affect other NGF-elicited cellular responses examined, including
NGF-dependent priming of cells, gp140prototrk autophosphorylation,
immediate-early gene induction, and phosphorylation of several known
cytoskeletal proteins (MAP 1.2/1B, chartin MAPs, and beta-tubulin).
However, phosphate incorporation into a cytoskeletally localized 58 kDa
phosphoprotein, designated pp58, is selectively reduced in KT5926-treated
cultures (+/- NGF). Although KT5926 is an in vitro inhibitor of myosin
light chain kinase and calmodulin-dependent protein kinase II, inhibition
of these two kinase activities by ML-9 and KN-62, respectively, applied
alone or together, does not mimic the effects of KT5926 on neurite growth
and on pp58 phosphorylation. Taken together, our findings suggest that
KT5926, via a previously unidentified protein kinase inhibitory activity,
differentially interferes with NGF-promoted growth cone function and
consequently affects neuritic outgrowth. This compound should therefore be
a useful tool for dissecting the mechanism of NGF actions and affords a
means to identify phosphoproteins that play specific roles in neurite
growth/elongation.