Department of Molecular Biology , Bristol-Myers Squibb Pharmaceutical Research Institute , Princeton , New Jersey 08543-4000 .
Oncogene 7 : 371-81 ( 1992)
Abstract
K252a , an efficient serine/threonine protein kinase inhibitor ( IC50s of to 30 nM ) , has been shown to block the neuronal differentiation of rat pheochromocytoma PC12 cells induced by nerve growth factor ( NGF ) .
In this report , we demonstrate that K252a is a potent inhibitor ( IC50 of 3 nM ) of the tyrosine protein kinase activity of the NGF receptor gp140trk , the product of the trk protooncogene .
K252a also inhibits the kinase activity of its transforming alleles , the trk oncogenes , and of the related neurotrophin receptors gp145trkB and gp145trkC , the products of the other known members of the trk gene family , trkB and trkC .
In contrast , K252a has no effect ( even at micromolar concentrations ) on other tyrosine protein kinases such as the receptors for EGF and PDGF and the products of the v-src and v-fms oncogenes .
In addition , K252a rapidly reverts the transformed phenotype of NIH3T3 cells transformed by either autocrine stimulation of the trk family of receptors by their cognate ligands or by expression of trk oncogenes isolated from human tumors .
The selectivity of K252a for the catalytic activity of the trk family of kinases should help to establish the structural basis for the rational design of highly specific tyrosine protein kinase inhibitors .
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Laboratorium fur Biochemie , Eidgenossische Technische Hochschule , Zurich , Switzerland .
J Cell Biol 116 : 1035-42 ( 1992)
Abstract
In bone forming cartilage in vivo , cells undergo terminal differentiation , whereas most of the cells in normal articular cartilage do not .
Chondrocyte hypertrophy can be induced also in vitro by diffusible signals .
We have identified growth factors or hormones acting individually on 17-d chick embryo sternal chondrocytes cultured in agarose gels under strictly serum-free conditions .
Insulin-like growth factor I or insulin triggered the first steps of chondrocyte maturation , i.e. , cell proliferation and increased matrix deposition while the chondrocytic phenotype was maintained .
However , cells did not progress to the hypertrophic stage .
Proliferation and stimulated collagen production was preceded by a lag period , indicating that synthesis of other components was required before cells became responsive to insulin-like growth factor I or insulin .
Very small amounts of FBS exerted effects similar to those of insulin-like growth factor I or insulin .
However , FBS could act directly and elicited hypertrophy when constituting greater than 1% of the culture media .
Basic FGF has been claimed to be the most potent chondrocyte mitogen , but had negligible effects under serum-free conditions .
The same is true for PDGF , a major serum-mitogen .
Under the direction of thyroxine , cells did not proliferate but became typical hypertrophic chondrocytes , extensively synthesizing collagen X and alkaline phosphatase .