The nuclear, 75 kDa form of early growth response protein-1/nerve growth factor-induced A protein is primarily restricted to LH beta-subunit-expressing cells in rat anterior pituitary.
OBJECTIVE
Early growth response protein-1 (Egr-1)/nerve growth factor-induced A (also known as Zif-268, Krox-24, TIS8, ZENK) is a zinc-finger transcription factor which, although expressed in a range of organ systems, has been shown to be essential only in the maintenance of fertility through actions within the endocrine system. In the present study we have investigated the anatomical basis for actions of Egr-1 in the adult anterior pituitary gland.


METHODS
Using female rats and mice as experimental models, we have used immunocytochemical and microscopic analysis to make observations of the cellular and sub-cellular localization of Egr-1 protein.


METHODS
Immuno-(Western) blotting was first used to characterize the anterior pituitary proteins detected by a commercially available Egr-1 antibody. Subsequently, the antibody was used both singly and in combination with an LH beta-subunit antibody, for immunocytochemical localization studies in pituitary sections.


RESULTS
The Egr-1 antiserum detected a single, major (primarily nuclear) 75 kDa protein band in Western blots of anterior pituitary extracts. Nuclear localization was confirmed by immunocytochemistry, which also demonstrated that the 75 kDa protein is localized to a minority sub-population of anterior pituitary cells in both rat and mouse. Dual immunocytochemical localization showed that the Egr-1 protein is primarily restricted to the nuclei of LH beta-subunit-expressing cells.


CONCLUSIONS
Sub-cellular localization of Egr-1 to the nucleus is consistent with a direct role in transcriptional regulation of anterior pituitary function in the adult rat. Furthermore, a selective role in the physiological control of gonadotrophin gene expression is indicated.
Knight
C
C
School of Biosciences, Cardiff University, Cardiff CF10 3US, UK.
Slade
J P
JP
Carter
D
D
D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure*; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000378:metabolism; D051766:Early Growth Response Protein 1; D004971:Estrus; D005260:Female; D017874:Immediate-Early Proteins; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000032:analysis*; D008970:Molecular Weight; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000032:analysis* / Q000378:metabolism; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D014157:Transcription Factors; D007986:Luteinizing Hormone