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1.
Biochem Biophys Res Commun ; 703: 149653, 2024 Apr 09.
Article in English | MEDLINE | ID: mdl-38364682

ABSTRACT

Cellular vesicle long-distance transport along the cytoplasmic actin network has recently been uncovered in several cell systems. In metaphase mouse oocytes, the motor protein myosin-5b (Myo5b) and the actin nucleation factor Spire are recruited to the Rab11a-positive vesicle membrane, forming a ternary complex of Myo5b/Spire/Rab11a that drives the vesicle long-distance transport to the oocyte cortex. However, the mechanism underlying the intermolecular regulation of the Myo5b/Spire/Rab11a complex remains unknown. In this study, we expressed and purified Myo5b, Spire2, and Rab11a proteins, and performed ATPase activity measurements, pulldown and single-molecule motility assays. Our results demonstrate that both Spire2 and Rab11a are required to activate Myo5b motor activity under physiological ionic conditions. The GTBM fragment of Spire2 stimulates the ATPase activity of Myo5b, while Rab11a enhances this activation. This activation occurs by disrupting the head-tail interaction of Myo5b. Furthermore, at the single-molecule level, we observed that the GTBM fragment of Spire2 and Rab11a coordinate to stimulate the Myo5b motility activity. Based on our results, we propose that upon association with the vesicle membrane, Myo5b, Spire2 and Rab11a form a ternary complex, and the inhibited Myo5b is synergistically activated by Spire2 and Rab11a, thereby triggering the long-distance transport of vesicles.


Subject(s)
Actins , Myosin Type V , Mice , Animals , Actins/metabolism , Myosins/metabolism , Actin Cytoskeleton/metabolism , Myosin Type V/metabolism , rab GTP-Binding Proteins/metabolism
2.
Cell Calcium ; 103: 102549, 2022 05.
Article in English | MEDLINE | ID: mdl-35144093

ABSTRACT

In Drosophila compound eyes, myosin-5 (DmMyo5) plays a key role in organelle transportation, including transporting pigment granules from the distal end to the proximal end of the photoreceptor cells to regulate the amount of light reaching the photosensitive membrane organelle rhabdomere. It is generally accepted that, upon exposure to light, the dark-adapted compound eyes produce a rapid rise of free Ca2+ concentration, which in turn activates DmMyo5 to transport pigment granules. Considering the dynamic and compartmentation of Ca2+ signaling in photoreceptor cells during light exposure, it is necessary to understand the kinetics of Ca2+ interaction with DmMyo5. Here, we investigated the interaction of Ca2+ with Drosophila calmodulin (CaM) in complex with the IQ1 of DmMyo5 using steady-state and kinetic approaches. Our results show that IQ1 binding substantially increases the Ca2+ affinity of CaM and decreases the dissociation rate of Ca2+ from CaM. In addition, we found that Mlc-C, the light chain associated with the IQ2 of DmMyo5, has little effect on the Ca2+ kinetics of CaM in IQ1. We propose that, by decreasing the Ca2+ dissociation rate from CaM, IQ1 delays the deactivation of DmMyo5 after Ca2+ transition, thereby prolonging the DmMyo5-driven transportation of pigment granules.


Subject(s)
Calcium , Calmodulin , Animals , Calcium/metabolism , Calmodulin/metabolism , Drosophila/metabolism , Myosins/chemistry , Myosins/metabolism , Protein Binding/physiology
3.
ACS Omega ; 5(34): 21815-21823, 2020 Sep 01.
Article in English | MEDLINE | ID: mdl-32905433

ABSTRACT

Phenamacril is a Fusarium-specific fungicide used for Fusarium head blight management. The target of phenamacril is FgMyo1, the sole class I myosin in Fusarium graminearum. The point mutation S217L in FgMyo1 is responsible for the high resistance of F. graminearum to phenamacril. Recent structural studies have shown that phenamacril binds to the 50 kDa cleft of the FgMyo1 motor domain, forming extensive interactions, including a hydrogen bond between the cyano group of phenamacril and the hydroxyl group of S217. Here, we produced FgMyo1IQ2, a truncated FgMyo1 composed of the motor domain and two IQ motifs complexed with the F. graminearum calmodulin in insect Sf9 cells. Phenamacril potently inhibited both the basal and the actin-activated ATPase activities of FgMyo1IQ2, with an IC50 in a micromolar range. S217 mutations of FgMyo1IQ2 substantially increased the IC50 of phenamacril. S217T or S217L each increased the IC50 of phenamacril for ∼60-fold, while S217A only increased the IC50 for ∼4-fold. These results indicate that the hydroxyl group of S217 plays an important, but nonessential role in phenamacril binding and that the bulky side chain at the position 217 sterically hinders phenamacril binding. On the other hand, S217P, which might alter the local conformation of the phenamacril-binding site, completely abolished the phenamacril inhibition. Because the cyano group of phenamacril does not form discernible interactions with FgMyo1 other than the nonessential hydrogen bond with the S217 hydroxyl group, we propose the cyano group of phenamacril as a key modification site for the development of novel fungicides.

4.
J Biol Chem ; 295(12): 3749-3756, 2020 03 20.
Article in English | MEDLINE | ID: mdl-31811090

ABSTRACT

Myosin-IC (Myo1c) has been proposed to function in delivery of glucose transporter type 4 (GLUT4)-containing vesicles to the plasma membrane in response to insulin stimulation. Current evidence suggests that, upon insulin stimulation, Myo1c is phosphorylated at Ser701, leading to binding of the signaling protein 14-3-3ß. Biochemical and functional details of the Myo1c-14-3-3ß interaction have yet to be described. Using recombinantly expressed proteins and mass spectrometry-based analyses to monitor Myo1c phosphorylation, along with pulldown, fluorescence binding, and additional biochemical assays, we show here that 14-3-3ß is a dimer and, consistent with previous work, that it binds to Myo1c in the presence of calcium. This interaction was associated with dissociation of calmodulin (CaM) from the IQ motif in Myo1c. Surprisingly, we found that 14-3-3ß binds to Myo1c independent of Ser701 phosphorylation in vitro Additionally, in contrast to previous reports, we did not observe Myo1c Ser701 phosphorylation by Ca2+/CaM-dependent protein kinase II (CaMKII), although CaMKII phosphorylated four other Myo1c sites. The presence of 14-3-3ß had little effect on the actin-activated ATPase or motile activities of Myo1c. Given these results, it is unlikely that 14-3-3ß acts as a cargo adaptor for Myo1c-powered transport; rather, we propose that 14-3-3ß binds Myo1c in the presence of calcium and stabilizes the calmodulin-dissociated, nonmotile myosin.


Subject(s)
14-3-3 Proteins/metabolism , Myosin Type I/metabolism , 14-3-3 Proteins/chemistry , 14-3-3 Proteins/genetics , Amino Acid Motifs , Calcium/chemistry , Calcium/metabolism , Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism , Calmodulin/metabolism , Dimerization , Egtazic Acid/chemistry , Humans , Mass Spectrometry , Myosin Type I/chemistry , Myosin Type I/genetics , Phosphorylation , Protein Binding , Recombinant Proteins/biosynthesis , Recombinant Proteins/chemistry , Recombinant Proteins/isolation & purification , Ultracentrifugation
5.
Biosci Rep ; 39(1)2019 01 31.
Article in English | MEDLINE | ID: mdl-30545898

ABSTRACT

Mammalian myosin-5b (Myo5b) plays a critical role in the recycling of endosomes to the plasma membrane via the interactions with Rab11a and the Rab11 family interacting protein 2 (FIP2). However, it remains unclear on how Rab11a and FIP2 are coordinated in tethering Myo5b with the vesicles and activating the motor function of Myo5b. In the present study, we show that Rab11a binds to the globular tail domain (GTD) of Myo5b and this binding abolishes the head-GTD interaction of Myo5b, thus activating the motor function of Myo5b. On the other hand, FIP2 directly interacts with both Rab11a and the tail of Myo5b, and the binding of FIP2 to Myo5b does not affect Myo5b motor function. Moreover, Rab11a displays higher affinity to FIP2 than to Myo5b, suggesting that Rab11a binds preferentially to FIP2 than to Myo5b. Based on the current findings, we propose that the association of Myo5b with vesicles is mediated by FIP2, which bridges Myo5b and the membrane-bound Rab11a, whereas the motor function of Myo5b is regulated by Rab11a.


Subject(s)
Myosins/metabolism , rab GTP-Binding Proteins/metabolism , Animals , Carrier Proteins/metabolism , Cell Line , Cell Membrane/metabolism , Endosomes/metabolism , Humans , Membrane Proteins/metabolism , Protein Binding/physiology , Protein Transport/physiology , Rats , Sf9 Cells
6.
Biochemistry ; 56(32): 4235-4243, 2017 08 15.
Article in English | MEDLINE | ID: mdl-28714309

ABSTRACT

Blebbistatin is a potent and specific inhibitor of the motor functions of class II myosins, including striated muscle myosin and nonmuscle myosin-2 (NM2). However, the blebbistatin inhibition of NM2c has not been assessed and remains controversial with respect to its efficacy with smooth muscle myosin (SmM), which is highly homologous to NM2. To clarify these issues, we analyzed the effects of blebbistatin on the motor activities of recombinant SmM and three NM2s (NM2a, -2b, and -2c). We found that blebbistatin potently inhibits the actin-activated ATPase activities of SmM and NM2s with following IC50 values: 6.47 µM for SmM, 3.58 µM for NM2a, 2.30 µM for NM2b, and 1.57 µM for NM2c. To identify the blebbistatin-resistant myosin-2 mutant, we performed mutagenesis analysis of the conserved residues in the blebbistatin-binding site of SmM and NM2s. We found that the A456F mutation renders SmM and NM2s resistant to blebbistatin without greatly altering their motor activities or phosphorylation-dependent regulation, making A456F a useful mutant for investigating the cellular function of NM2s.


Subject(s)
Avian Proteins/antagonists & inhibitors , Avian Proteins/chemistry , Heterocyclic Compounds, 4 or More Rings/chemistry , Nonmuscle Myosin Type IIB/antagonists & inhibitors , Nonmuscle Myosin Type IIB/chemistry , Smooth Muscle Myosins/antagonists & inhibitors , Smooth Muscle Myosins/chemistry , Amino Acid Substitution , Animals , Avian Proteins/genetics , Avian Proteins/metabolism , Chickens , Humans , Mice , Mutation, Missense , Nonmuscle Myosin Type IIB/genetics , Nonmuscle Myosin Type IIB/metabolism , Smooth Muscle Myosins/genetics , Smooth Muscle Myosins/metabolism
7.
Biochem J ; 469(1): 135-44, 2015 Jul 01.
Article in English | MEDLINE | ID: mdl-25940004

ABSTRACT

In the Drosophila melanogaster compound eye, myosin-5 (DmM5) plays two distinct roles in response to light stimulation: transport of pigment granules to the rhabdomere base to decrease light exposure and transport of rhodopsin-bearing vesicles to the rhabdomere base to compensate for the rhodopsin loss during light exposure. However, little is known of how the motor function of DmM5 is regulated at the molecular level. In the present study, we overexpressed DmM5 in Sf9 insect cells and investigated its regulation using purified proteins. We found that the actin-activated ATPase activity of DmM5 is significantly lower than that of the truncated DmM5 having the C-terminal globular tail domain (GTD) deleted, indicating that the GTD is the inhibitory domain. The actin-activated ATPase activity of DmM5 is significantly activated by micromolar levels of calcium. DmM5 associates with pigment granules and rhodopsin-bearing vesicles through cargo-binding proteins Lightoid (Ltd) and dRab11 respectively. We found that GTP-bound dRab11, but not Ltd, significantly activates DmM5 actin-activated ATPase activity. Moreover, we identified Gln(1689) in the GTD as the critical residue for the interaction with dRab11 and activation of DmM5 motor function by dRab11. Based on those results, we propose that DmM5-dependent transport of pigment granules is directly activated by light-induced calcium influx and the DmM5-dependent transport of rhodopsin-bearing vesicle is activated by active GTP-bound dRab11, whose formation is stimulated by light-induced calcium influx.


Subject(s)
Calcium Signaling/physiology , Calcium/metabolism , Drosophila Proteins/metabolism , Myosins/metabolism , Rhodopsin/metabolism , rab GTP-Binding Proteins/metabolism , Animals , Drosophila Proteins/genetics , Drosophila melanogaster , Guanosine Triphosphate/genetics , Guanosine Triphosphate/metabolism , Myosins/genetics , Rhodopsin/genetics , Sf9 Cells , Spodoptera , rab GTP-Binding Proteins/genetics
8.
Environ Microbiol ; 17(8): 2735-46, 2015 Aug.
Article in English | MEDLINE | ID: mdl-25404531

ABSTRACT

Fusarium head blight (FHB) caused by Fusarium graminearum is a devastating disease of cereal crops worldwide. Recently, a novel fungicide JS399-19 has been launched into the marketplace to manage FHB. It is compelling that JS399-19 shows highly inhibitory activity towards some Fusarium species, but not to other fungi, indicating that it is an environmentally compatible fungicide. To explore the mode of action of this species-specific compound, we conducted a whole-genome transcript profiling together with genetic and biochemical assays, and discovered that JS399-19 targets the myosin I of F. graminearum (FgMyo1). FgMyo1 is essential for F. graminearum growth. A point mutation S217L or E420K in FgMyo1 is responsible for F. graminearum resistance to JS399-19. In addition, transformation of F. graminearum with the myosin I gene of Magnaporthe grisea, the causal agent of rice blast, also led to JS399-19 resistance. JS399-19 strongly inhibits the ATPase activity of the wild-type FgMyo1, but not the mutated FgMyo1(S217L/E420K) . These results provide us a new insight into the design of species-specific antifungal compounds. Furthermore, our strategy can be applied to identify novel drug targets in various pathogenic organisms.


Subject(s)
Amino Acids/pharmacology , Antifungal Agents/pharmacology , Fungicides, Industrial/pharmacology , Fusarium/genetics , Myosin Type I/antagonists & inhibitors , Phenylpropionates/pharmacology , Adenosine Triphosphatases/antagonists & inhibitors , Edible Grain/microbiology , Fusarium/drug effects , Fusarium/pathogenicity , Gene Expression Profiling , Magnaporthe/genetics , Myosin Type I/genetics , Plant Diseases/microbiology
9.
J Biol Chem ; 289(26): 18535-48, 2014 Jun 27.
Article in English | MEDLINE | ID: mdl-24825904

ABSTRACT

Class XIX myosin (Myo19) is a vertebrate-specific unconventional myosin, responsible for the transport of mitochondria. To characterize biochemical properties of Myo19, we prepared recombinant mouse Myo19-truncated constructs containing the motor domain and the IQ motifs using the baculovirus/Sf9 expression system. We identified regulatory light chain (RLC) of smooth muscle/non-muscle myosin-2 as the light chain of Myo19. The actin-activated ATPase activity and the actin-gliding velocity of Myo19-truncated constructs were about one-third and one-sixth as those of myosin-5a, respectively. The apparent affinity of Myo19 to actin was about the same as that of myosin-5a. The RLCs bound to Myo19 could be phosphorylated by myosin light chain kinase, but this phosphorylation had little effect on the actin-activated ATPase activity and the actin-gliding activity of Myo19-truncated constructs. Using dual fluorescence-labeled actin filaments, we determined that Myo19 is a plus-end-directed molecular motor. We found that, similar to that of the high-duty ratio myosin, such as myosin-5a, ADP release rate was comparable with the maximal actin-activated ATPase activity of Myo19, indicating that ADP release is a rate-limiting step for the ATPase cycle of acto-Myo19. ADP strongly inhibited the actin-activated ATPase activity and actin-gliding activity of Myo19-truncated constructs. Based on the above results, we concluded that Myo19 is a high-duty ratio molecular motor moving to the plus-end of the actin filament.


Subject(s)
Actins/metabolism , Adenosine Diphosphate/metabolism , Amino Acid Sequence , Animals , Kinetics , Mice , Mitochondria/chemistry , Mitochondria/genetics , Mitochondria/metabolism , Molecular Sequence Data , Myosin Heavy Chains/genetics , Myosin Heavy Chains/metabolism , Myosin Type V/genetics , Myosin Type V/metabolism , Myosins , Sequence Alignment
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