Isoproterenol downregulation of statin-related gene expression in the rat parotid gland.
Statin, a 57 kilodalton (kDa) nuclear protein, is characteristically found in nonproliferating cells in culture as well as nondividing cells of a wide range of highly differentiated tissues. Moreover, cells in culture that are statin positive lose this statin expression when re-entering the cell-cycle traverse. In this work, statin expression was investigated in the parotid gland of untreated rats and those treated with isoproterenol (IPR), a proliferation-inducing catecholamine. Indirect immunofluorescence microscopy revealed specific nuclear staining with anti-statin monoclonal antibody (S-44) in the acinar and ducts cells of the untreated rats but significantly reduced in those induced with isoproterenol. To characterize the protein recognized by S-44, protein extracts from both tissues were immunoblotted and incubated with S-44. The antibody reacted specifically with a 48 kDa protein in the extract of the parotid glands from untreated rats while no reaction was detected in that of the proliferation-induced ones. These observations along with the result that a statin-like (S1) transcript is downregulated by isoproterenol in the parotid glands further support the notion that the disappearance of statin-related expression is associated with the IPR-induced proliferation in the rat parotid glands. The discrepancy between the apparent molecular mass of the protein identified by S-44 in nonproliferating parotid cells and that of statin originally found in fibroblasts, suggests that either a modified form of statin may be present in the parotid gland, or this 48 kDa protein may be a member of the nonproliferative statin-like family.
Ann
D K
DK
Department of Pharmacology, University of Minnesota, Medical School, Minneapolis 55455.
Wechsler
A
A
Lin
H H
HH
Wang
E
E
D000818:Animals; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D015536:Down-Regulation; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D009687:Nuclear Proteins; D010306:Parotid Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D011506:Proteins; D012333:RNA, Messenger; D007545:Isoproterenol