Myosin Vs organize actin cables in fission yeast

Presti, Libera Lo; Chang, Fred; Martin, Sophie G.

doi:10.1091/mbc.e12-07-0499

Cited by 46 publications

(90 citation statements)

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“…Some actin filaments and small bundles of filaments persisted on the lateral borders of rings throughout constriction (Figure 1A arrow) [26, 29]. Myo51 localized along For3p-dependent actin cables during interphase [23] giving a filamentous appearance in the cytoplasm (Figure 1A arrow). Beginning at time zero Myo51p concentrated in a narrow equatorial band and in filamentous structures between nodes [30] around the middle of the cell (Figures 1A asterisk and 1B), both dependent on actin filaments [23].…”

Section: Resultsmentioning

confidence: 99%

“…Myo51 localized along For3p-dependent actin cables during interphase [23] giving a filamentous appearance in the cytoplasm (Figure 1A arrow). Beginning at time zero Myo51p concentrated in a narrow equatorial band and in filamentous structures between nodes [30] around the middle of the cell (Figures 1A asterisk and 1B), both dependent on actin filaments [23]. Myp2 began to accumulate in fully formed contractile rings at time +20 min (Figures 1A asterisk and 1B) [25].…”

Section: Resultsmentioning

confidence: 99%

“…Myp2 began to accumulate in fully formed contractile rings at time +20 min (Figures 1A asterisk and 1B) [25]. Myo52 transports cargo including vesicles with Bgs1 β-1,3-glucan synthase along actin filament cables during interphase and mitosis, but does not concentrate in the contractile ring [14, 23, 24, 31–33]. We confirmed previous observations [32, 33] that the Δ myo52 strain grows slowly at both 25°C and 36°C, that the Δ myo52 mutation did not enhance the myo2-E1 growth defect at either temperature, but that Δ myo52 is synthetically lethal with Δ myp2 at 36°C (Figure S1A).…”

Section: Resultsmentioning

confidence: 99%

“…Myo51 and Myo52 carry cargo along actin filament cables, a crucial contribution to cell polarity [14]. During cell division Myo51 redistributes from actin cables to the equator [23], and Myo52 transports vesicles containing beta-glucan synthetase Bgs1 along actin cables to the forming septum (but does not concentrate in the contractile ring) [24]. Both type V myosins require actin for their localization [23].…”

Section: Introductionmentioning

confidence: 99%

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Three Myosins Contribute Uniquely to the Assembly and Constriction of the Fission Yeast Cytokinetic Contractile Ring

et al. 2015

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Summary Cytokinesis in fission yeast cells depends on conventional myosin-II (Myo2) to assemble and constrict a contractile ring of actin filaments. Less is known about the functions of an unconventional myosin-II (Myp2) and a myosin-V (Myo51) that are also present in the contractile ring. Myo2 appears in cytokinetic nodes around the equator 10 min before spindle pole body separation (cell cycle time −10 min) independent of actin filaments, followed by Myo51 at time zero and Myp2 at time +20 min, both located between nodes and dependent on actin filaments. We investigated the contributions of these three myosins to cytokinesis using a severely disabled mutation of the essential myosin-II heavy chain gene (myo2-E1) and deletion mutations of the other myosin heavy chain genes. Cells with only Myo2 assemble contractile rings normally. Cells with either Myp2 or Myo51 alone can assemble nodes and actin filaments into contractile rings, but complete assembly later than normal. Both Myp2 and Myo2 contribute to constriction of fully assembled rings at rates 55% of normal in cells relying on Myp2 alone and 25% of normal in cells with Myo2 alone. Myo51 alone cannot constrict rings but increases the constriction rate by Myo2 in Δmyp2 cells or Myp2 in myo2-E1 cells. Three myosins function in a hierarchal, complementary manner to accomplish cytokinesis with Myo2 and Myo51 taking the lead during contractile ring assembly and Myp2 making the greatest contribution to constriction.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Three Myosins Contribute Uniquely to the Assembly and Constriction of the Fission Yeast Cytokinetic Contractile Ring

et al. 2015

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“…After switching to medium containing 2% 2-DG, actin cables can still be observed in bni1-11 bnr1 Δ cells at 35 °C (Figures 4E and 4F), indicating that actin polymerization is not necessary for cable stabilization. Additionally, it has been shown that myosin Vs contributes to actin cables organization in fission yeast [28]. Since Myo2 is immobilized on actin cables upon glucose depletion, it is possible that Myo2 helps to stabilize them.…”

Section: Resultsmentioning

confidence: 99%

Rapid Glucose Depletion Immobilizes Active Myosin V on Stabilized Actin Cables

Bretscher

2014

Current Biology

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Summary Polarization of eukaryotic cells requires organelles and protein complexes to be transported to their proper destinations along the cytoskeleton [1]. When nutrients are abundant, budding yeast grows rapidly transporting secretory vesicles for localized growth and actively segregating organelles [2, 3]. This is mediated by myosin-Vs transporting cargos along F-actin bundles known as actin cables [4]. Actin cables are dynamic structures regulated by assembly, stabilization and disassembly [5]. Polarized growth and actin filament dynamics consume energy. For most organisms, glucose is the preferred energy source and generally represses alternative carbon source usage [6]. Thus upon abrupt glucose depletion, yeast shuts down pathways consuming large amounts of energy, including the vacuolar-ATPase [7, 8], translation [9] and phosphoinositide metabolism [10]. Here we show that glucose withdrawal rapidly (<1 min) depletes ATP levels and the yeast myosin V, Myo2, responds by relocalizing to actin cables, making it the fastest response documented. Myo2 immobilized on cables releases its secretory cargo, defining a new rigor-like state of a myosin-V in vivo. Only actively transporting Myo2 can be converted to the rigor-like state. Glucose depletion has differential effects on the actin cytoskeleton resulting in disassembly of actin patches with concomitant inhibition of endocytosis, and strong stabilization of actin cables, thereby revealing a selective and previously unappreciated ATP requirement for actin cable disassembly. A similar response is seen in HeLa cells to ATP depletion. These findings reveal a new fast-acting energy conservation strategy halting growth by immobilizing myosin-V in a newly described state on selectively stabilized actin cables.

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Myosin motor isoforms direct specification of actomyosin function by tropomyosins

et al. 2015

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Myosins and tropomyosins represent two cytoskeletal proteins that often work together with actin filaments in contractile and motile cellular processes. While the specialized role of tropomyosin in striated muscle myosin-II regulation is well characterized, its role in non-muscle myosin regulation is poorly understood. We previously showed that fission yeast tropomyosin (Cdc8p) positively regulates myosin-II (Myo2p) and myosin-V (Myo52p) motors. To understand the broader implications of this regulation we examined the role of two mammalian tropomyosins (Tpm3.1cy/Tm5NM1 and Tpm4.2cy/Tm4) recently implicated in cancer cell proliferation and metastasis. Like Cdc8p, the Tpm3.1cy and Tpm4.2cy isoforms significantly enhance Myo2p and Myo52p motor activity, converting non-processive Myo52p molecules into processive motors that can walk along actin tracks as single molecules. In contrast to the positive regulation of Myo2p and Myo52p, Cdc8p and the mammalian tropomyosins potently inhibited skeletal muscle myosin-II, while having negligible effects on the highly processive mammalian myosin-Va. In support of a conserved role for certain tropomyosins in regulating non-muscle actomyosin structures, Tpm3.1cy supported normal contractile ring function in fission yeast. Our work reveals that actomyosin regulation by tropomyosin is dependent on the myosin isoform, highlighting a general role for specific isoforms of tropomyosin in sorting myosin motor outputs.

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Myosin Vs organize actin cables in fission yeast

Cited by 46 publications

References 58 publications

Three Myosins Contribute Uniquely to the Assembly and Constriction of the Fission Yeast Cytokinetic Contractile Ring

Three Myosins Contribute Uniquely to the Assembly and Constriction of the Fission Yeast Cytokinetic Contractile Ring

Rapid Glucose Depletion Immobilizes Active Myosin V on Stabilized Actin Cables

Myosin motor isoforms direct specification of actomyosin function by tropomyosins

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