Previous work in our laboratory has indicated translocation of prolactin (PRL) to the nucleus upon receptor internalization. To identify potential PRL-binding proteins that may facilitate this translocation, interactive screening was performed. These screens identified a member of the immunophilin family, cyclophilin B (CypB), as interacting with PRL. The cyclophilins are a family of peptidyl-prolyl isomerases (PPI) that serve as protein chaperones and mediate the immunosuppressive effects of cyclosporin A (CsA). Our data demonstrate that the interaction of CypB with PRL and another somatolactogenic hormone, growth hormone (GH), is enhanced in the presence of CsA. This interaction results in a ten-fold increase in PRL-driven proliferation and a significant increase in the retrotranslocation of PRL into the nucleus, an event that is abrogated by the removal of a putative nuclear localization signal sequence in the amino-terminal of CypB. Therefore, it is hypothesized that CypB-PRL interaction facilitates PRL internalization and assists in its translocation to the nucleus. This hypothesis will be tested by two specific aims using PRL-responsive lymphoid and breast cancer cell lines. First, the interaction, composition, and function of the CypB/PRL/PRLr complex will be determined by biochemical and mutagenic approaches. Second, the mechanisms and functional consequences of CypB/PRL internalization will be examined through pulse-chase studies using biochemical and electron microscopic approaches in conjunction with CypB and PRLr mutants. These studies will provide significant new insight into the physiological role of the cyclophilins and further define the mechanisms through which PR/PRLr internalization are mediated in PRL-responsive tissues.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
1F32DK010043-01
Application #
6070087
Study Section
Endocrinology Study Section (END)
Program Officer
Hyde, James F
Project Start
2000-04-01
Project End
Budget Start
2000-04-01
Budget End
2001-03-31
Support Year
1
Fiscal Year
2000
Total Cost
$37,516
Indirect Cost
Name
University of Pennsylvania
Department
Pathology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Rycyzyn, Michael A; Clevenger, Charles V (2002) The intranuclear prolactin/cyclophilin B complex as a transcriptional inducer. Proc Natl Acad Sci U S A 99:6790-5
Rycyzyn, M A; Reilly, S C; O'Malley, K et al. (2000) Role of cyclophilin B in prolactin signal transduction and nuclear retrotranslocation. Mol Endocrinol 14:1175-86
Rycyzyn, M A; Clevenger, C V (2000) Role of cyclophilins in somatolactogenic action. Ann N Y Acad Sci 917:514-21