Parathyroid hormone promotes the disassembly of cytoskeletal actin and myosin in cultured osteoblastic cells: Mediation by cyclic AMP

Journal Article · Tue Jan 01 00:00:00 EST 1991 · Journal of Cellular Biochemistry; (USA)

DOI:https://doi.org/10.1002/jcb.240450117· OSTI ID:5946731

Egan, J J; Gronowicz, G; Rodan, G A ^[1]

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1. National Institutes of Diabetes, Digestive, and Kidney Diseases, Bethesda, MD (USA)

Parathyroid hormone (PTH) alters the shape of osteoblastic cells both in vivo and in vitro. In this study, we examined the effect of PTH on cytoskeletal actin and myosin, estimated by polyacrylamide gel electrophoresis of Triton X-100 (1%) nonextractable proteins. After 2-5 minutes, PTH caused a rapid and transient decrease of 50-60% in polymerized actin and myosin associated with the Triton X-100 nonextractable cytoskeleton. Polymerized actin returned to control levels by 30 min. The PTH effect was dose-dependent with an IC50 of about 1 nM, and was partially inhibited by the (3-34) PTH antagonist. PTH caused a rapid transient rise in cyclic AMP (cAMP) in these cells that peaked at 4 min, while the nadir in cytoskeletal actin and myosin was recorded around 5 min. The intracellular calcium chelator Quin-2/AM (10 microM) also decreased cytoskeletal actin and myosin, to the same extent as did PTH (100 nM). To distinguish between cAMP elevation and Ca++ reduction as mediators of PTH action, we measured the phosphorylation of the 20 kD (PI 4.9) myosin light chain in cells preincubated with (32P)-orthophosphate. The phosphorylation of this protein decreased within 2-3 min after PTH addition and returned to control levels after 5 min. The calcium ionophore A-23187 did not antagonize this PTH effect. Visualization of microfilaments with rhodamine-conjugated phalloidin showed that PTH altered the cytoskeleton by decreasing the number of stress fibers. These changes in the cytoskeleton paralleled changes in the shape of the cells from a spread configuration to a stellate form with retracting processes. The above findings indicate that the alteration in osteoblast shape produced by PTH involve relatively rapid and transient changes in cytoskeletal organization that appear to be mediated by cAMP.

• OSTI ID: 5946731
• Journal Information: Journal of Cellular Biochemistry; (USA), Vol. 45:1; ISSN 0730-2312
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ACTIN
PHOSPHORYLATION
AMP
BIOCHEMICAL REACTION KINETICS
BONE CELLS
MORPHOLOGY
MYOSIN
PARATHORMONE
AUTORADIOGRAPHY
CELL CULTURES
CHELATING AGENTS
DOSE-RESPONSE RELATIONSHIPS
ELECTROPHORESIS
PHOSPHORUS 32
POLYMERIZATION
RATS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL REACTIONS
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
GLOBULINS
HORMONES
ISOTOPES
KINETICS
LIGHT NUCLEI
MAMMALS
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PEPTIDE HORMONES
PHOSPHORUS ISOTOPES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RODENTS
SOMATIC CELLS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques