The primitive bio-defence system by Ca2+ in a lower eukaryote Physarum polycephalum

The acellular slime mold Physarum polycephalum is a gigantic amoeba with multiple nuclei. The cell body usually shows vigorous cytoplasmic streaming that supplies nourishment in the whole cell by the vein as a blood vessel. For single cell, the damage of a cell causes death of the individual. For ex...

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Veröffentlicht in:Journal of Pharmacological Sciences 2003, Vol.91 (suppl.2), p.281-281
Hauptverfasser: Akio Nakamura, Yuki Hanyuda, Xin Hong, Kazuhiro Kohama
Format: Artikel
Sprache:jpn
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Zusammenfassung:The acellular slime mold Physarum polycephalum is a gigantic amoeba with multiple nuclei. The cell body usually shows vigorous cytoplasmic streaming that supplies nourishment in the whole cell by the vein as a blood vessel. For single cell, the damage of a cell causes death of the individual. For example, when the vein was stabbed with a micro-needle, the cytoplasm flows out. However, the cytoplasm which flowed out stopped immediately. It is a just like blood coagulation of higher animal. This clotting system was inhibited by Ca2+ chelator as EGTA, indicating the importance of Ca2+ for this system. We have recently cloned three Ca2+ -binding proteins with respect to this system. The 40 kDa Ca2+- binding protein (CBP40) expressed abundantly in the Physarum plasmodia. CBP40 can self-assemble by Ca2+ above μM level. Annexin is Ca2+ and lipid-binding protein that bound CBP40 in vitro. Transglutaminase (TGase) cross-linked CBP40 as a specific in situ substrate. To understand the physiological significance of the self- assembly of CBP40, we examined the localization of CBP40 and the related proteins within the plasmodia. CBP40, annexin and TGase were found in a cellular region immediately beneath the plasma membrane. CBP40 and annexin were concentrated in regions where cell membrane injury took place. CBP40 may thus function as a barrier for preventing the outflow of cytoplasm by self- assembly and TGase may make the CBP40 barrier firm, and finally annexin restores the plasma membrane.
ISSN:1347-8613