Insulin stimulates accumulation and efflux of macromolecules in isolated nuclei from H35 hepatoma cells.
This study used 10-nm gold particles with 5-7 insulin molecules attached (Au10-Ins) to investigate the site of interaction of insulin with the nuclear envelope during insulin uptake into intact isolated nuclei. Despite its size, and in the absence of ATP, Au10-Ins entered nuclei through the nuclear pore and associated with the heterochromatin. Because Au10-Ins is essentially gold-bovine serum albumin (Au-BSA) with a few insulin molecules attached, the effect of insulin and other growth factors on the nuclear accumulation of BSA coupled to 10-, 15-, and 24-nm-diam colloidal gold particles (Au10-BSA, Au15-BSA, and Au24-BSA) was determined. The Au-BSA complexes were excluded from nuclei in the absence of insulin. Insulin (0.5-100 ng/ml) caused a dose-dependent accumulation of Au10-BSA in the nucleus. The nuclear membrane was shown to be intact by several criteria, therefore, accumulation of Au-BSA occurred via the nuclear pore and was not due to leakage across or through the membrane. Uptake of 15- and 24-nm Au-BSA molecules was not affected by insulin, suggesting the hormone had a limited effect in increasing the functional diameter of the nuclear pores. Glucagon, epidermal growth factor, platelet-derived growth factor, insulinlike growth factor I, and insulin A or B chains did not stimulate the accumulation of Au10-BSA. The insulin-stimulated accumulation of Au10-BSA was blocked by concanavalin A, mimicked by wheat-germ agglutinin, and did not require ATP. The Au10-BSA in the nucleus was associated with heterochromatin, suggesting it bound to a nuclear element.(ABSTRACT TRUNCATED AT 250 WORDS)
Soler
A P
AP
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia.
Smith
R M
RM
Jarett
L
L
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism; D003102:Colloids; D004305:Dose-Response Relationship, Drug; D006046:Gold / Q000494:pharmacology*; D006133:Growth Substances / Q000494:pharmacology; D007328:Insulin / Q000493:pharmacokinetics / Q000494:pharmacology*; D037102:Lectins / Q000502:physiology; D046911:Macromolecular Substances; D012710:Serum Albumin, Bovine / Q000493:pharmacokinetics; D014407:Tumor Cells, Cultured
D003102:Colloids; D006133:Growth Substances; D007328:Insulin; D037102:Lectins; D046911:Macromolecular Substances; D012710:Serum Albumin, Bovine; C005147:5'-adenylyl (beta,gamma-methylene)diphosphonate; D006046:Gold; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate