Naslov
Protein phosphatase 2A, a potential regulator of actin dynamics and actin-based organelle motility in the green alga Acetabularia

Autori
Menzel, Diedrik ; Vugrek, Oliver ; Frank, Stefan ; Elsner-Menzel, Christine

Izvornik
European journal of cell biology (0171-9335) 67 (1995), 2; 179-187

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Acetabularia ; actin ; cytoskeleton ; okadaic acid

Sažetak
The gaint, unicellular ulgu Acetubuluriu is a well known experimental model for the study of actin-dependent intracellular organelle motility. In the cyst stage, however, which is equivalent to the gametophytic slage, organelles are immobile, even though an actin cytoskeleton is present. The reason for the lack of organelle motility at this stage has not been known. To test the hypothesis that organelle motility could be under the control of posttranslational modification by protein phosphorylation, we have treated cysts with submicromolar concentrations of okadaic acid or calyculin A, both potent inhibitors of serine/threonine protein phosphatases (ser/thr- PPases). The effects were dramatic: Instead of linear actin bundles typicul for control cysts, circular arrays of actin bundles Cormed in the cortical cyst cytoplasm. Concomitant with the formation oC these action rings, the cytoplasmic layers beneath the rings began to slowly rotate in a continnous and uniform counter-clockwisefashion. This effect suggests that protein phosphorylation acts on the actin cytoskeleton at two levels: (1) It changes the assembly properties oC the actin filament system to the extent that novelcytoskeletal configurations arc Cormed and (2) it raises the activity of putative motor proteins involved in the rotational movements to levels sufficiently high to support motility at a stage when organelle motility does not normally occur. Northern blot analysis of cyst stagemRNA using probes specific to protein phosphatase type 1 (PPl) and type 2A (PP2A) reveals that PP2A is strongly expressed at this developmental stage whereas PPI is not detectable, suggesting that PP2A is the likely target to the protein phosphatase inhibitors. As a first step in analyzingthese regulatory proteins on the molecular level, we describe the complete sequence of a cyst-specific PP2A cDNA clone.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA