Hormonally-regulated expression of voltage-operated Ca(2+) channels in osteocytic (MLO-Y4) cells.
Voltage operated calcium channels (VOCCs) are important in stimulus-response coupling in osteoblasts. We have investigated the expression of VOCCs in the mouse osteocyte cell line, MLO-Y4. Using the whole-cell patch clamp technique we were unable to detect any VOCC currents (n = 436) even in the presence of the L-type VOCC agonist Bay K 8644 (n = 350). Reverse transcription polymerase chain reaction (RT-PCR), using primers to detect alpha(1C), alpha(1D), and alpha(1G) VOCC subunits (all of which are expressed in primary osteoblasts), did not generate detectable products with mRNA from MLO-Y4 cells. However, after treatment with physiological levels of hormones, VOCC alpha(1) subunit mRNAs were detected in MLO-Y4 cells. PTH, 17beta-estradiol, and dexamethasone-treatment induced expression of L-type (alpha(1C), alpha(1D)) subunit transcripts. ATP-treatment induced expression of T-type (alpha(1G)) transcripts. Using whole-cell patch clamp we detected VOCC currents in 5-10% of cells after treatment. Current characteristics (L- or T-type) were consistent with the transcript expressed.
Gu
Y
Y
School of Bioscience, University of Birmingham, Birmingham, Edgbaston, B15 2TT, United Kingdom.
Preston
M R
MR
Magnay
J
J
El Haj
A J
AJ
Publicover
S J
SJ
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006728:Hormones / Q000494:pharmacology*; D051379:Mice; D010011:Osteocytes / Q000187:drug effects* / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D021122:Protein Subunits; D020133:Reverse Transcriptase Polymerase Chain Reaction
D015220:Calcium Channels; D017931:DNA Primers; D006728:Hormones; D010281:Parathyroid Hormone; D021122:Protein Subunits; D004958:Estradiol; D003907:Dexamethasone; D000255:Adenosine Triphosphate