Endoplasmic reticulum calcium storage and release in cells expressing misfolded growth hormone.
OBJECTIVE
Deletion of amino acids 32-71 in human growth hormone (Delta 32-71-GH) causes severe autosomal dominant GH deficiency. These experiments test whether retention of Delta 32-71-GH in the endoplasmic reticulum (ER) lumen leads to aberrant Ca(2+) regulation.


METHODS
COS cells were transfected with Delta 32-71-GH, wild-type-GH or empty plasmid, and the ability of the cells to release Ca(2+) from the ER and transmit a Ca(2+) signal to the cytoplasm was investigated using cytoplasmic Ca(2+) dyes and ER-targeted cameleon Ca(2+) reporters.


RESULTS
Resting free Ca(2+), the rate of Ca(2+) release from the ER and the size of the ionophore-releasable ER Ca(2+) pool were not altered by Delta 32-71-GH. Stimulation of endogenous Ca(2+)-mobilizing receptors for histamine and thrombin resulted in similar changes in cytoplasmic and ER Ca(2+) in cells expressing wild-type and Delta 32-71-GH.


CONCLUSIONS
Ca(2+) regulation is preserved despite retention of misfolded GH in the ER.
Graves
Thomas K
TK
Department of Pharmacology and Physiology, University of Rochester Medical Center, Box 711, 601 Elmwood Avenue, Rochester, NY 14642, USA.
Hinkle
Patricia M
PM
D000818:Animals; D019556:COS Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D019382:Human Growth Hormone / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007124:Immunoenzyme Techniques; D007476:Ionophores / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D017510:Protein Folding; D021381:Protein Transport; D017384:Sequence Deletion; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007476:Ionophores; D010446:Peptide Fragments; D019382:Human Growth Hormone; D019284:Thapsigargin; D002118:Calcium