Structural and functional effects of hydrostatic pressure on centrosomes from vertebrate cells

In an attempt to better understand the role of centrioles in vertebrate cen trosomes, hydrostatic pressure was applied to isolated centrosomes as a mea ns to disassemble centriole microtubules. Treatments of the centrosomes wer e monitored by analyzing their protein composition, ultrastructure, their a bility to nucleate microtubules from pure tubulin, and their capability to induce parthenogenetic development of Xenopus eggs. Moderate hydrostatic pr essure (95 MPa) already affected the organization of centriole microtubules in isolated centrosomes, and also impaired microtubule nucleation. At high er pressure, the protein composition of the peri-centriolar matrix (PCM) wa s also altered and the capacity to nucleate microtubules severely impaired. Incubation of the treated centrosomes in Xenopus egg extract could restore their capacity to nucleate microtubules after treatment at 95 MPa, but not after higher pressure treatment. However, the centriole structure was in n o case restored. It is noteworthy that centrosomes treated with mild pressu re did not allow parthenogenetic development after injection into Xenopus e ggs, even if they had recovered their capacity to nucleate microtubules. Th is suggested that, in agreement with previous results, centrosomes in which centriole architecture is impaired, could not direct the biogenesis of new centrioles in Xenopus eggs. Centriole structure could also be affected by applying mild hydrostatic pressure directly to living cells. Comparison of the effect of hydrostatic pressure on cells at the G1/S border or on the co rresponding cytoplasts suggests that pro-centrioles are very sensitive to p ressure. However, cells can regrow a centriole after pressure-induced disas sembly. In that case, centrosomes eventually recover an apparently normal d uplication cycle although with some delay. (C) 2001 Wiley-Liss, Inc.