Role of actin and Myo2p in polarized secretion and growth of Saccharomyces cerevisiae.
We examined the role of the actin cytoskeleton in secretion in Saccharomyces cerevisiae with the use of several quantitative assays, including time-lapse video microscopy of cell surface growth in individual living cells. In latrunculin, which depolymerizes filamentous actin, cell surface growth was completely depolarized but still occurred, albeit at a reduced level. Thus, filamentous actin is necessary for polarized secretion but not for secretion per se. Consistent with this conclusion, latrunculin caused vesicles to accumulate at random positions throughout the cell. Cortical actin patches cluster at locations that correlate with sites of polarized secretion. However, we found that actin patch polarization is not necessary for polarized secretion because a mutant, bee1Delta(las17Delta), which completely lacks actin patch polarization, displayed polarized growth. In contrast, a mutant lacking actin cables, tpm1-2 tpm2Delta, had a severe defect in polarized growth. The yeast class V myosin Myo2p is hypothesized to mediate polarized secretion. A mutation in the motor domain of Myo2p, myo2-66, caused growth to be depolarized but with only a partial decrease in the level of overall growth. This effect is similar to that of latrunculin, suggesting that Myo2p interacts with filamentous actin. However, inhibition of Myo2p function by expression of its tail domain completely abolished growth.
Karpova
T S
TS
Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri 63110, USA.
Reck-Peterson
S L
SL
Elkind
N B
NB
Mooseker
M S
MS
Novick
P J
PJ
Cooper
J A
JA
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D016764:Cell Polarity; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018715:Microscopy, Video / Q000379:methods; D009154:Mutation; D018995:Myosin Heavy Chains; D024462:Myosin Type II; D024701:Myosin Type V; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002352:Carrier Proteins; D005656:Fungal Proteins; D008164:Luminescent Proteins; C077512:MYO2 protein, S cerevisiae; C434211:MYO2 protein, S pombe; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D013844:Thiazoles; D053778:Thiazolidines; D049452:Green Fluorescent Proteins; D024462:Myosin Type II; D024701:Myosin Type V; D018995:Myosin Heavy Chains; C037067:latrunculin A