Open AccessPhosphorylation of Ribosomal Protein S6 Mediates Mammalian Target of Rapamycin Complex 1–Induced Parathyroid Cell Proliferation in Secondary Hyperparathyroidism
Author(s) -
Oded Volovelsky,
Gili Cohen,
Ariel Kenig,
Gilad Wasserman,
Avigail Dreazen,
Oded Meyuhas,
Justin Silver,
Tally Naveh-Many
Publication year - 2016
Publication title -
journal of the american society of nephrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.451
H-Index - 279
eISSN - 1533-3450
pISSN - 1046-6673
DOI - 10.1681/asn.2015040339
Subject(s) - ribosomal protein s6 , endocrinology , medicine , mtorc1 , secondary hyperparathyroidism , hyperparathyroidism , parathyroid hormone , uremia , cell growth , pi3k/akt/mtor pathway , rptor , phosphorylation , biology , p70 s6 kinase 1 , signal transduction , microbiology and biotechnology , calcium , biochemistry
Secondary hyperparathyroidism is characterized by increased serum parathyroid hormone (PTH) level and parathyroid cell proliferation. However, the molecular pathways mediating the increased parathyroid cell proliferation remain undefined. Here, we found that the mTOR pathway was activated in the parathyroid of rats with secondary hyperparathyroidism induced by either chronic hypocalcemia or uremia, which was measured by increased phosphorylation of ribosomal protein S6 (rpS6), a downstream target of the mTOR pathway. This activation correlated with increased parathyroid cell proliferation. Inhibition of mTOR complex 1 by rapamycin decreased or prevented parathyroid cell proliferation in secondary hyperparathyroidism rats and in vitro in uremic rat parathyroid glands in organ culture. Knockin rpS6(p-/-) mice, in which rpS6 cannot be phosphorylated because of substitution of all five phosphorylatable serines with alanines, had impaired PTH secretion after experimental uremia- or folic acid-induced AKI. Uremic rpS6(p-/-) mice had no increase in parathyroid cell proliferation compared with a marked increase in uremic wild-type mice. These results underscore the importance of mTOR activation and rpS6 phosphorylation for the pathogenesis of secondary hyperparathyroidism and indicate that mTORC1 is a significant regulator of parathyroid cell proliferation through rpS6.