Hypergravity signal transduction in HeLa cells with concomitant phosphorylation of proteins immunoprecipitated with anti-microtubule-associated protein antibodies.
We have shown that hypergravity (35g) stimulates production of inositol 1,4,5-trisphosphate (IP3) and decreases adenosine 3',5'-cyclic monophosphate (cAMP) levels in HeLa cells. IP3 production rapidly increased 1.5- and 2.1-fold greater (P less than 0.05) than the control after 2- and 5-min exposures to 35g, respectively. The intracellular cAMP levels, determined in the presence of isobutylmethylxanthine, were decreased by 11% (P less than 0.05) and 16% (P less than 0.01) relative to the control after 10- and 20-min exposures to 35g, respectively. The phosphorylation of proteins which were immunoprecipitated by antibodies recognizing microtubule-associated proteins (ipMAPs) was also apparent after exposure of these cells to hypergravity. In the detergent-insoluble fraction, phosphorylation of a 115-kDa protein was significantly enhanced compared to the control after a 5-min exposure to 35g. In the detergent-soluble fraction, phosphorylation of a 200-kDa protein was observed served after a 20-min exposure to 35g. Our study suggests that IP3 and cAMP may act as second messengers in hypergravity signal transduction. Phosphorylation of ipMAPs in both the detergent-soluble and -insoluble fractions suggests that cytoskeletal structures may be influenced by gravity.
Department of Biomaterials Science, Faculty of Dentistry, Tokyo Medical and Dental University.
Y
Y
Kumei
P A
PA
Whitson
A
A
Sato
N M
NM
Cintrón
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000911:Antibodies, Monoclonal; D002498:Centrifugation; D000242:Cyclic AMP / Q000378:metabolism; D006112:Gravitation; D006367:HeLa Cells; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D000911:Antibodies, Monoclonal; D008869:Microtubule-Associated Proteins; D010750:Phosphoproteins; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine