It is all about timing and location : coordination of calcium signaling controls cell migration
- Feng-Chiao Tsai.
- Aug. 2012.
- Physical description
- online resource (xxv, 170 pages) : illustrations (some color)
- Tsai, Feng-Chiao.
- Axelrod, Jeffrey (Jeffrey David). thesis advisor.
- Chen, James Kenneth. thesis advisor.
- Meyer, Tobias. thesis advisor (primary).
- Nelson, W. J. (W. James) thesis advisor.
- Stanford University. Program in Cancer Biology.
- Stanford University. Committee on Graduate Studies. degree grantor.
- Includes bibliographical references.
- Terminating cell migration is critical for cancer treatment, because malignancy progresses through migrating tumor cells (metastasis) and migrating endothelial cells (neoangiogenesis.) Although cell migration requires Ca2+ for polarity and turning, it is not well understood how Ca2+ signals regulate cell migration. By studying sheet migration using endothelial cells loaded with Fura-2/AM, we identified pulsatile local Ca2+ pulses near the cell front. Each Ca2+ pulse controlled a local retraction and adhesion process in lamellipodia. Eliminating endogenous Ca2+ pulses reduced lamellipodial retraction while photo-release of Ca2+ from NP-EGTA induced front retraction and adhesion, indicating that these small Ca2+ signals were both necessary and sufficient for cyclic lamellipodia activity. Mechanistically, these local Ca2+ pulses acts through myosin light-chain kinase and myosin II to mediate actin cable retraction and to strengthen focal adhesion. We further explored the origin of these local Ca2+ signals. Removing extracellular Ca2+ did not eliminate local Ca2+ pulses, suggesting that these local signals are generated from activated inositol-3-phosphate receptors (IP3R) in the endoplasmic reticulum (ER). Inhibiting receptor tyrosine kinases (RTK) diminished local Ca2+ pulses, confirming that RTK-induced IP3R activation was the major source of these Ca2+ signals. More experiments demonstrated that diacylglycerol, the downstream regulator of RTK signaling, was also enriched in the cell front. It contributed to cell motility and polarity through protein kinase C. Therefore, polarized RTK signaling generates local Ca2+ signals and diacylglycerol in the cell front to ensure coordinated cell movement. We also investigated how Ca2+ homeostasis was maintained during cell migration. Our data showed that plasma membrane Ca2+ ATPases (PMCA) pumped Ca2+ out of the cell more actively in the front than in the back. The resulting low basal Ca2+ in the front of migrating cells maintained the sensitivity of the cell front to local Ca2+ pulses. Furthermore, to avoid depletion of Ca2+ in the front ER after it being released through IP3R, microtubules transported STIM1, a sensor of ER luminal Ca2+, toward the cell front triggering store-operated Ca2+ influx near the leading edge. Thus, cells maintain efficient migration through coordinated Ca2+ signaling systems. In summary, temporal-spatial coordination of Ca2+ signaling controls cell migration by regulating local adhesion, motility, and polarization. Our research also reveals the importance of interactions between signaling modules in migrating cells. Finally, a "synthetic immobility" screen will elucidate how different components are coordinated in cell migration, and will identify novel drug targets against cancer metastasis.
- Publication date
- Submitted to the Program in Cancer Biology and the Committee on Graduate Studies of Stanford University.
- Thesis (Ph.D.)--Stanford University, 2012.