RT Journal Article
SR Electronic
T1 Calcium nanodomains in spindles
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 404715
DO 10.1101/404715
A1 Guolong Mo
A1 Ruizhen Li
A1 Zachary Swider
A1 Yong Tao
A1 Katsuhiko Mikoshiba
A1 William M. Bement
A1 X. Johné Liu
YR 2018
UL http://biorxiv.org/content/early/2018/08/30/404715.abstract
AB The role of calcium signaling in specific events of animal cell meiosis or mitosis (M-phase) is a subject of enduring controversy. Early efforts suggested that increases in intracellular free calcium ([Ca2+]i) promote spindle disassembly 1, 2 while subsequent work suggested that global [Ca2+]i increases trigger nuclear envelope breakdown, spindle assembly, the metaphase-anaphase transition, and cytokinesis 3-6. However, further studies led to the conclusion that elevation of [Ca2+]i either has no role in these events, plays a permissive role in these events, or functions as an auxiliary signaling pathway that supplements other mechanisms 7. One potential explanation of the controversy is that specific M-phase events might depend on highly localized increases in [Ca2+]i, variously referred to as microdomains 8 or nanodomains 9, as proposed recently 10. Such domains are hypothesized to arise from rapid shuttling of calcium between closely positioned sources and sinks, rendering them potentially difficult to detect with traditional dyes and largely insensitive to slow chelators such as EGTA 9. Here a novel microtubule-binding calcium sensor—TubeCamp--was used to test the hypothesis 10 that spindles are associated with calcium nanodomains. TubeCamp imaging revealed that spindles in Xenopus eggs, Xenopus embryos, and HeLa cells were all associated with calcium nanodomains at the spindle poles. Calcium nanodomains also formed in spindles assembled in cell extracts and at the center of monopolar spindles, suggesting that they are a basic feature of spindle self-assembly. Disruption of calcium nanodomains via perturbation of inositol-1,4,5-trisphosphate signaling or rapid chelation of [Ca2+]i resulted in spindle disassembly in vivo and vitro. The results demonstrate the existence of spindle-associated calcium nanodomains and indicate that such domains are an essential and common feature of spindles in vertebrates.