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Regulation of expression of collagenase‐3 in normal, differentiating rat osteoblasts
Author(s) -
Winchester Sandra K.,
Bloch Sharon R.,
Fiacco Gerald J.,
Partridge Nicola C.
Publication year - 1999
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199912)181:3<479::aid-jcp12>3.0.co;2-d
Subject(s) - collagenase , medicine , ionomycin , endocrinology , cycloheximide , protein kinase c , parathyroid hormone , cyclic adenosine monophosphate , activator (genetics) , protein kinase a , biology , alkaline phosphatase , chemistry , kinase , calcium , microbiology and biotechnology , protein biosynthesis , enzyme , biochemistry , receptor , stimulation
We investigated the regulation of collagenase‐3 expression in normal, differentiating rat osteoblasts. Fetal rat calvarial cell cultures showed an increase in alkaline phosphatase activity reaching maximal levels between 7–14 days postconfluence, then declining with the onset of mineralization. Collagenase‐3 mRNA was just detectable after proliferation ceased at day 7, increased up to day 21, and declined at later ages. Postconfluent cells maintained in nonmineralizing medium expressed collagenase‐3 but did not show the developmental increase exhibited by cells switched to mineralization medium. Cells maintained in nonmineralizing medium continued to proliferate; cells in mineralization medium ceased proliferation. In addition, collagenase‐3 mRNA was not detected in subcultured cells allowed to remineralize. These results suggest that enhanced accumulation of collagenase‐3 mRNA is triggered by cessation of proliferation or acquisition of a mineralized extracellular matrix and that other factors may also be required. After initiation of basal expression, parathyroid hormone (PTH) caused a dose‐dependent increase in collagenase‐3 mRNA. Both the cyclic adenosine monophosphate (cAMP) analogue, 8‐bromo‐cAMP (8‐Br‐cAMP), and the protein kinase C (PKC) activator, phorbol myristate acetate, increased collagenase‐3 expression, while the calcium ionophore, ionomycin, did not, suggesting that PTH was acting through the protein kinase A (PKA) and PKC pathways. Inhibition of protein synthesis with cycloheximide caused an increase in basal collagenase‐3 expression but blocked the effect of PTH, suggesting that an inhibitory factor prevents basal expression while an inductive factor is involved with PTH action. In summary, collagenase‐3 is expressed in mineralized osteoblasts and cessation of proliferation and initiation of mineralization are triggers for collagenase‐3 expression. PTH also stimulates expression of the enzyme through both PKA and PKC pathways in the mineralizing osteoblast. J. Cell. Physiol. 181:479–488, 1999. © 1999 Wiley‐Liss, Inc.