Endogenous Autoinhibitors Regulate Changes in Actin Tyrosine Phosphorylation During Dictyostelium Spore Germination

Gauthier, Mona L.; Lydan, Michael A.; O’Day, Danton H.; Cotter, David A.

doi:10.1016/s0898-6568(96)00113-1

Cited by 26 publications

(18 citation statements)

References 25 publications

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“…The extent of actin phosphorylation at Tyr-53 varies dramatically during the different stages of the developmental cycle of Dictyostelium cells (9)(10)(11). Biochemically, actin Tyr-53 phosphorylation had been shown to increase the critical concentration for polymerization, reduce the rates of nucleation and pointed end elongation, and decrease the affinity for DNase I (11).…”

Section: Discussionmentioning

confidence: 99%

“…In none of these examples, however, is the precise connection between actin phosphorylation and cytoskeleton remodeling well understood. Such a connection is better established in Dictyostelium cells, in which the developmental cycle correlates closely with the extent of actin tyrosine phosphorylation (6)(7)(8)(9)(10)(11).…”

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confidence: 99%

“…The extent of actin phosphorylation, which is very low in growing vegetative cells, begins to increase [12][13][14][15][16][17][18][19][20][21][22][23][24] h into the developmental cycle, reaching Ϸ50% of the total actin at Ϸ36 h (9)(10)(11). At this high level of actin phosphorylation, the spores of the mature fruiting bodies remain viable for Ϸ20 days, at which time viability and actin phosphorylation levels both decrease, disappearing entirely by Ϸ30 days.…”

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confidence: 99%

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Modulation of actin structure and function by phosphorylation of Tyr-53 and profilin binding

Baek

Xiong

Ferrón

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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On starvation, Dictyostelium cells aggregate to form multicellular fruiting bodies containing spores that germinate when transferred to nutrient-rich medium. This developmental cycle correlates with the extent of actin phosphorylation at Tyr-53 (pY53-actin), which is low in vegetative cells but high in viable mature spores. Here we describe high-resolution crystal structures of pY53-actin and unphosphorylated actin in complexes with gelsolin segment 1 and profilin. In the structure of pY53-actin, the phosphate group on Tyr-53 makes hydrogen-bonding interactions with residues of the DNase I-binding loop (D-loop) of actin, resulting in a more stable conformation of the D-loop than in the unphosphorylated structures. A more rigidly folded D-loop may explain some of the previously described properties of pY53-actin, including its increased critical concentration for polymerization, reduced rates of nucleation and pointed end elongation, and weak affinity for DNase I. We show here that phosphorylation of Tyr-53 inhibits subtilisin cleavage of the D-loop and reduces the rate of nucleotide exchange on actin. The structure of profilin-Dictyostelium-actin is strikingly similar to previously determined structures of profilin-␤-actin and profilin-␣-actin. By comparing this representative set of profilin-actin structures with other structures of actin, we highlight the effects of profilin on the actin conformation. In the profilin-actin complexes, subdomains 1 and 3 of actin close around profilin, producing a 4.7°rotation of the two major domains of actin relative to each other. As a result, the nucleotide cleft becomes moderately more open in the profilin-actin complex, probably explaining the stimulation of nucleotide exchange on actin by profilin.actin phosphorylation ͉ profilin-actin structure ͉ pY53-actin structure ͉ Dictyostelium discoideum actin ͉ gelsolin-actin structure

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Modulation of actin structure and function by phosphorylation of Tyr-53 and profilin binding

Baek

Xiong

Ferrón

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…The conservation of Tyr-53 is particularly striking because the immediately adjacent DNase I-binding loop (D-loop) 2 in subdomain 2, originally defined as residues 40 -50 (2), is one of the actin regions in which mutations are most common. It may be relevant that Tyr-53 is dynamically phosphorylated when Dictyostelium amoebae are subjected to stress (3)(4)(5)(6) and during the developmental cycle, accounting for 50% of the actin in spores (7)(8)(9)(10), and rapidly dephosphorylated prior to spore germination. Tyr-phosphorylated actin also occurs in cysts of Acanthamoeba (10) and in Mimosa petioles, where dephosphorylation accompanies leaf folding (11,12), and mass spectroscopic data indicate the presence of Tyr-53 phosphorylated actin in cultured cancer cells (13).…”

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confidence: 99%

Mutation of Actin Tyr-53 Alters the Conformations of the DNase I-binding Loop and the Nucleotide-binding Cleft

Liu

Shu

Hong

et al. 2010

Journal of Biological Chemistry

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All but 11 of the 323 known actin sequences have Tyr at position 53, and the 11 exceptions have the conservative substitution Phe, which raises the following questions. What is the critical role(s) of Tyr-53, and, if it can be replaced by Phe, why has this happened so infrequently? We compared the properties of purified endogenous Dictyostelium actin and mutant constructs with Tyr-53 replaced by Phe, Ala, Glu, Trp, and Leu. The Y53F mutant did not differ significantly from endogenous actin in any of the properties assayed, but the Y53A and Y53E mutants differed substantially; affinity for DNase I was reduced, the rate of nucleotide exchange was increased, the critical concentration for polymerization was increased, filament elongation was inhibited, and polymerized actin was in the form of small oligomers and imperfect filaments. Growth and/or development of cells expressing these actin mutants were also inhibited. The Trp and Leu mutations had lesser but still significant effects on cell phenotype and the biochemical properties of the purified actins. We conclude that either

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“…pY-actin appears late in maturing spores, i.e., Ϸ24 h into the developmental cycle, reaches a maximum level at Ϸ36 h, at which time Ϸ50% of the actin is phosphorylated (3), remains constant for Ϸ20 days, at 22°C, and then decreases, disappearing entirely by 30 days, at which time the spores are no longer viable (3). When viable spores are placed in nutrient medium, pY-actin is dephosphorylated, with a half-life of Ϸ5 min (3), before spore swelling and germination (2,4).…”

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Phosphorylation of actin Tyr-53 inhibits filament nucleation and elongation and destabilizes filaments

Liu¹,

Shu²,

Hong³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Dictyostelium actin was shown to become phosphorylated on Tyr-53 late in the developmental cycle and when cells in the amoeboid stage are subjected to stress but the phosphorylated actin had not been purified and characterized. We have separated phosphorylated and unphosphorylated actin and shown that Tyr-53 phosphorylation substantially reduces actin's ability to inactivate DNase I, increases actin's critical concentration, and greatly reduces its rate of polymerization. Tyr-53 phosphorylation substantially, if not completely, inhibits nucleation and elongation from the pointed end of actin filaments and reduces the rate of elongation from the barbed end. Negatively stained electron microscopic images of polymerized Tyr-53-phosphorylated actin show a variable mixture of small oligomers and filaments, which are converted to more typical, long filaments upon addition of myosin subfragment 1. Tyr-53-phosphorylated and unphosphorylated actin copolymerize in vitro, and phosphorylated and unphosphorylated actin colocalize in amoebae. Tyr-53 phosphorylation does not affect the ability of filamentous actin to activate myosin ATPase.actin polymerization ͉ Dictyostelium ͉ phosphorylated actin T ransfer of Dictyostelium amoebae from nutrient to nonnutrient medium initiates a 24-hour developmental cycle (1) in which the amoebae aggregate and differentiate to form multicellular organisms that mature to fruiting bodies containing stable spores from which, when they are placed in nutrient medium, amoebae germinate. Several laboratories (2-4) reported tyrosine phosphorylation of actin [phosphotyrosine actin (pY-actin)] correlated with rearrangements of the actin cytoskeleton during the developmental cycle. pY-actin appears late in maturing spores, i.e., Ϸ24 h into the developmental cycle, reaches a maximum level at Ϸ36 h, at which time Ϸ50% of the actin is phosphorylated (3), remains constant for Ϸ20 days, at 22°C, and then decreases, disappearing entirely by 30 days, at which time the spores are no longer viable (3). When viable spores are placed in nutrient medium, pY-actin is dephosphorylated, with a half-life of Ϸ5 min (3), before spore swelling and germination (2, 4).Although vegetative amoebae in nutrient medium contain little or no pY-actin (5, 6), phosphorylation transiently increases (for Ϸ20-25 min) when amoebae are transferred from nonnutrient to nutrient medium (7), with concurrent changes in cell shape, for example, loss of pseudopods, rounding up of the previously elongated cells, and weakened adherence to the substratum (7). Tyrosine phosphorylation also occurs when vegetative amoebae in nutrient medium are exposed to phenylarsine oxide (PAO) (5), an inhibitor of phosphotyrosine phosphatase, or are subjected to stress, for example, inhibition of oxidative phosphorylation (8, 9) or elevated temperature (9), with parallel changes in cell shape similar to the changes that occur when cells are transferred from nonnutrient to nutrient medium.Importantly, phosphorylation occurs uniquely at Tyr-53 (9). Thus, phosphoryl...

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Endogenous Autoinhibitors Regulate Changes in Actin Tyrosine Phosphorylation During Dictyostelium Spore Germination

Cited by 26 publications

References 25 publications

Modulation of actin structure and function by phosphorylation of Tyr-53 and profilin binding

Modulation of actin structure and function by phosphorylation of Tyr-53 and profilin binding

Mutation of Actin Tyr-53 Alters the Conformations of the DNase I-binding Loop and the Nucleotide-binding Cleft

Phosphorylation of actin Tyr-53 inhibits filament nucleation and elongation and destabilizes filaments

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