Open AccessThe insulin‐stimulated receptor kinase is a tyrosine‐specific casein kinase
Author(s) -
ZICK Yehiel,
REESJONES Robert W.,
GRUNBERGER George,
TAYLOR Simeon I.,
MONCADA Victoria,
GORDEN Phillip,
ROTH Jesse
Publication year - 1983
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1983.tb07872.x
Subject(s) - insulin receptor , irs2 , insulin receptor substrate , tropomyosin receptor kinase c , insulin like growth factor 1 receptor , biochemistry , receptor tyrosine kinase , tyrosine kinase , ror1 , casein kinase 2 , insulin , chemistry , biology , mitogen activated protein kinase kinase , kinase , receptor , protein kinase a , platelet derived growth factor receptor , endocrinology , insulin resistance , growth factor
Insulin stimulates a kinase that phosphorylates tyrosines in the insulin receptor; this kinase is tightly associated with the insulin receptor itself. We now show that the insulin‐stimulated casein kinase, present in solubilized, lectin‐purified receptor preparations from rat liver, is indistinguishable from the insulin receptor kinase. As with phosphorylation of the insulin receptor, insulin selectively enhanced by 2–3‐fold the phosphorylation of tyrosines in casein. The insulin‐stimulated activities of both kinases were inactivated at 37°C with the same t 0.5 of 5 min and were identically affected by alkylating agents. Both receptor and casein kinase activities were specifically coprecipitated by anti‐receptor antibodies or by insulin and anti‐insulin antibodies. When the latter type of immune complexes were incubated with an excess of insulin, both kinase activities were quantitatively recovered. We therefore conclude that insulin‐stimulated receptor and casein phosphorylations are probably catalyzed by a single enzyme which is tightly associated with the receptor itself. Now, by replacing casein for receptor as substrate, it is possible to measure the enzymatic activity of this receptor‐related kinase itself, i.e. independent of the receptor as substrate. Detection of this activity is improved in the presence of certain alkylating agents. Use of artificial substrates (in combination with alkylating agents) is particularly important to dissect the functional components of the receptor complex, to study mechanisms of enzyme regulation and especially in situations where the available receptor for study is limited, e.g. fresh or cultured cells from patients.