Open AccessCell‐specific expression and function of adenylyl cyclases in rat pituitary tumour cell lines
Author(s) -
PAULSSEN Ruth H.,
JOHANSEN Per W.,
GORDELADZE Jan O.,
NYMOEN Øystein,
PAULSSEN Eyvind J.,
GAUTVIK Kaare M.
Publication year - 1994
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1994.tb18846.x
Subject(s) - cell culture , biology , vasoactive intestinal peptide , anterior pituitary , adenylyl cyclase , cell type , medicine , microbiology and biotechnology , endocrinology , calmodulin , pituitary gland , cell , chemistry , receptor , hormone , neuropeptide , biochemistry , stimulation , genetics , enzyme
The present study demonstrates cell‐specific distribution and describes distinct functional regulation of different adenylyl cyclases (AC, types I–VI) in rat pituitary cell tumor cell lines (GH 1 2C 1 , GH 3 and GH 4 C 1 cells) and pituitary tissue. Northern‐blot analysis revealed a distinct pattern of cell‐specific expression of the different AC types; Ca 2+ /calmodulin (CaM)‐insensitive AC type II was found in all cell lines tested except GH 1 2C 1 cells. The Ca 2+ ‐inhibitable AC type VI was found in all cell types tested. We observed a lack of the Ca 2+ /CaM‐sensitive AC type I in GH 3 and GH 4 C 1 cells. GH 1 2C 1 cells exclusively contained both Ca 2+ /CaM‐sensitive AC types I and III, the latter previously believed to be specific for olfactory tissue. An additional transcript of AC type III was found in rat brain and rat liver tissue. AC type IV, which is Ca 2+ /CaM insensitive, could be detected in the prolactin‐producing GH 3 and GH 4 C 1 cells and pituitary tissue but not in growth‐hormone‐producing GH 1 2C 1 cells. Basal and vasoactive‐intestinal‐peptide‐(VIP)‐releasing‐hormone, somatostatin (SRIF) and thyrothropin‐releasing‐hormone (TRH)‐modulation of AC activity was measured in the presence of 100 μM EGTA, anti‐CaM serum (dilution 1:2000) or 10 μM trifluoroperazine. Antisera against guanine‐nucleotide‐binding protein (G‐protein) α subunits (G i‐2 α, G s α) and β subunits (Gβ 35/36 ) and CaM were added for functional studies of the SRIF and VIP‐modulated AC in GH 1 2C 1 and GH 3 cells. These experiments indicate that the VIP and the SRIF receptors are coupled to a Ca 2+ /CaM‐sensitive AC in GH 1 2C 1 cells, different from the AC involved in the regulation of cAMP levels in GH 3 and GH 4 C 1 cells. In addition, the βγ‐complex is possibly able to modulate SRIF‐inhibited AC activity by potentiating the inhibitory effect. The TRH receptor in GH 3 and GH 4 C 1 cells is coupled to a Ca 2+ /CaM‐sensitive AC which is different from the already cloned forms of AC types I and III. We, therefore, conclude that hormone regulation of pituitary tumour cell functions differs between the GH cell lines, due to specific utilisation of AC types.