scholarly journals Phosphoinositide-binding proteins mark, shape and functionally modulate highly-diverged endocytic compartments in the parasitic protist Giardia lamblia

2020 ◽  
Vol 16 (2) ◽  
pp. e1008317
Author(s):  
Lenka Cernikova ◽  
Carmen Faso ◽  
Adrian B. Hehl
Keyword(s):  
Giardia Lamblia ◽  
Binding Proteins ◽  
Parasitic Protist ◽  
Endocytic Compartments

scholarly journals Phosphoinositide-binding proteins mark, shape and functionally modulate highly-diverged endocytic compartments in the parasitic protist Giardia lamblia

2019 ◽  
Author(s):  
Lenka Cernikova ◽  
Carmen Faso ◽  
Adrian B. Hehl
Keyword(s):  
Giardia Lamblia ◽  
Fluid Phase ◽  
Membrane Lipid ◽  
Model Systems ◽  
Coated Vesicle ◽  
New Members ◽  
Partial Conservation ◽  
Parasitic Protist ◽  
Organelle Morphology ◽  
Endocytic Compartments

AbstractPhosphorylated derivatives of phosphatidylinositol (PIPs), are key membrane lipid residues involved in clathrin-mediated endocytosis (CME). CME relies on PI(4,5)P2 to mark endocytic sites at the plasma membrane (PM) associated to clathrin-coated vesicle (CCV) formation. The highly diverged parasitic protist Giardia lamblia presents disordered and static clathrin assemblies at PM invaginations, contacting specialized endocytic organelles called peripheral vacuoles (PVs). The role for clathrin assemblies in fluid phase uptake and their link to internal membranes via PIP-binding adaptors is unknown.Here we provide evidence for a robust link between clathrin assemblies and fluid-phase uptake in G. lamblia mediated by proteins carrying predicted PX, FYVE and NECAP1 PIP-binding modules. We show that chemical and genetic perturbation of PIP-residue binding and turnover elicits novel uptake and organelle-morphology phenotypes. A combination of co-immunoprecipitation and in silico annotation techniques expands the initial PIP-binding network with addition of new members. Our data indicate that, despite the partial conservation of lipid markers and protein cohorts known to play important roles in dynamic endocytic events in well-characterized model systems, the Giardia lineage presents a strikingly divergent clathrin-centered network. This includes several PIP-binding modules, often associated to domains of currently unknown function that shape and modulate fluid-phase uptake at PVs.

Overlapping genes in parasitic protist Giardia lamblia

Gene ◽  
2001 ◽  
Vol 280 (1-2) ◽  
pp. 163-167 ◽  
Author(s):  
Naoyuki Iwabe ◽  
Takashi Miyata
Keyword(s):  
Giardia Lamblia ◽  
Overlapping Genes ◽  
Parasitic Protist

scholarly journals Localization of low molecular weight GTP binding proteins to exocytic and endocytic compartments

Cell ◽  
1990 ◽  
Vol 62 (2) ◽  
pp. 317-329 ◽  
Author(s):  
Philippe Chavrier ◽  
Robert G. Parton ◽  
Hans Peter Hauri ◽  
Kai Simons ◽  
Marino Zerial
Keyword(s):  
Molecular Weight ◽  
Binding Proteins ◽  
Low Molecular Weight ◽  
Gtp Binding Proteins ◽  
Gtp Binding ◽  
Endocytic Compartments

scholarly journals Variant-specific surface proteins of Giardia lamblia are zinc-binding proteins.

1993 ◽  
Vol 90 (12) ◽  
pp. 5489-5493 ◽  
Author(s):  
T. E. Nash ◽  
M. R. Mowatt
Keyword(s):  
Specific Surface ◽  
Giardia Lamblia ◽  
Binding Proteins ◽  
Surface Proteins ◽  
Zinc Binding

scholarly journals 14-3-3 Negatively Regulates Actin Filament Formation in the Deep Branching Eukaryote Giardia lamblia

2017 ◽  
Author(s):  
Jana Krtková ◽  
Jennifer Xu ◽  
Marco Lalle ◽  
Melissa Steele-Ogus ◽  
Germain C. M. Alas ◽  
...  
Keyword(s):  
Complex Formation ◽  
Actin Cytoskeleton ◽  
Actin Filament ◽  
Giardia Lamblia ◽  
Actin Filaments ◽  
Binding Proteins ◽  
Negative Regulator ◽  
Actin Binding ◽  
Filament Formation ◽  
Rho Family

AbstractThe phosphoserine/phosphothreonine-binding protein 14-3-3 is known to regulate actin, this function has been previously attributed to sequestration of phosphorylated cofilin. The deep branching eukaryote Giardia lamblia lacks cofilin and all other canonical actin-binding proteins (ABPs), and 14-3-3 was identified as an actin-associated protein in Giardia, yet its role in actin regulation was unknown. Gl14-3-3 depletion resulted in an overall disruption of actin organization characterized by ectopically distributed short actin filaments. Using phosphatase and kinase inhibitors, we demonstrated that actin phosphorylation correlated with destabilization of the actin network and increased complex formation with 14-3-3, while blocking actin phosphorylation stabilized actin filaments and attenuated complex formation. Giardia's sole Rho family GTPase, GlRac, modulates Gl14-3-3's association with actin, providing the first connection between GlRac and the actin cytoskeleton in Giardia. Giardia actin contains two putative 14-3-3 binding motifs, one of which (S330) is conserved in mammalian actin. Mutation of these sites reduced, but did not completely disrupt, the association with 14-3-3. Native gels and overlay assays indicate that intermediate proteins are required to support complex formation between 14-3-3 and actin. Overall, our results support a role for 14-3-3 as a negative regulator of actin filament formation.ImportanceGiardia lacks canonical actin binding proteins. 14-3-3 was identified as an actin interactor but the significance of this interaction was unknown. Loss of 14-3-3 results in ectopic short actin filaments, indicating that 14-3-3 is an important regulator of the actin cytoskeleton in Giardia. Drug studies indicate that 14-3-3 complex formation is in part phospho-regulated. We demonstrate that complex formation is downstream of Giardia’s sole Rho family GTPase, GlRac, this result provides the first mechanistic connection between GlRac and actin in Giardia. Native gels and overlay assays indicate intermediate proteins are required to support the interaction between 14-3-3 and actin suggesting that 14-3-3 is regulating multiple actin complexes. Overall, we find that 14-3-3 is a negative regulator of actin filament formation in Giardia.

scholarly journals 14-3-3 Regulates Actin Filament Formation in the Deep-Branching Eukaryote Giardia lamblia

mSphere ◽  
2017 ◽  
Vol 2 (5) ◽  
Author(s):  
Jana Krtková ◽  
Jennifer Xu ◽  
Marco Lalle ◽  
Melissa Steele-Ogus ◽  
Germain C. M. Alas ◽  
...  
Keyword(s):  
Complex Formation ◽  
Actin Cytoskeleton ◽  
Giardia Lamblia ◽  
Actin Filaments ◽  
Binding Proteins ◽  
Actin Binding ◽  
Actin Binding Proteins ◽  
Important Regulator ◽  
Rho Family ◽  
Drug Studies

ABSTRACT Giardia lacks canonical actin-binding proteins. Gl-14-3-3 was identified as an actin interactor, but the significance of this interaction was unknown. Loss of Gl-14-3-3 results in ectopic short actin filaments, indicating that Gl-14-3-3 is an important regulator of the actin cytoskeleton in Giardia. Drug studies indicate that Gl-14-3-3 complex formation is in part phospho-regulated. We demonstrate that complex formation is downstream of Giardia’s sole Rho family GTPase, Gl-Rac. This result provides the first mechanistic connection between Gl-Rac and Gl-actin in Giardia. Native gels and overlay assays indicate intermediate proteins are required to support the interaction between Gl-14-3-3 and Gl-actin, suggesting that Gl-14-3-3 is regulating multiple Gl-actin complexes. The phosphoserine/phosphothreonine-binding protein 14-3-3 is known to regulate actin; this function has been previously attributed to sequestration of phosphorylated cofilin. 14-3-3 was identified as an actin-associated protein in the deep-branching eukaryote Giardia lamblia; however, Giardia lacks cofilin and all other canonical actin-binding proteins (ABPs). Thus, the role of G. lamblia 14-3-3 (Gl-14-3-3) in actin regulation was unknown. Gl-14-3-3 depletion resulted in an overall disruption of actin organization characterized by ectopically distributed short actin filaments. Using phosphatase and kinase inhibitors, we demonstrated that actin phosphorylation correlated with destabilization of the actin network and increased complex formation with 14-3-3, while blocking actin phosphorylation stabilized actin filaments and attenuated complex formation. Giardia’s sole Rho family GTPase, Gl-Rac, modulates Gl-14-3-3’s association with actin, providing the first connection between Gl-Rac and the actin cytoskeleton in Giardia. Giardia actin (Gl-actin) contains two putative 14-3-3 binding motifs, one of which (S330) is conserved in mammalian actin. Mutation of these sites reduced, but did not completely disrupt, the association with 14-3-3. Native gels and overlay assays indicate that intermediate proteins are required to support complex formation between 14-3-3 and actin. Overall, our results support a role for 14-3-3 as a regulator of actin; however, the presence of multiple 14-3-3–actin complexes suggests a more complex regulatory relationship than might be expected for a minimalistic parasite. IMPORTANCE Giardia lacks canonical actin-binding proteins. Gl-14-3-3 was identified as an actin interactor, but the significance of this interaction was unknown. Loss of Gl-14-3-3 results in ectopic short actin filaments, indicating that Gl-14-3-3 is an important regulator of the actin cytoskeleton in Giardia. Drug studies indicate that Gl-14-3-3 complex formation is in part phospho-regulated. We demonstrate that complex formation is downstream of Giardia’s sole Rho family GTPase, Gl-Rac. This result provides the first mechanistic connection between Gl-Rac and Gl-actin in Giardia. Native gels and overlay assays indicate intermediate proteins are required to support the interaction between Gl-14-3-3 and Gl-actin, suggesting that Gl-14-3-3 is regulating multiple Gl-actin complexes.

High resolution spot scan imaging of frozen, hydrated actin bundles with 400kV electrons

1992 ◽  
Vol 50 (1) ◽  
pp. 512-513
Author(s):  
J. Jakana ◽  
M.F. Schmid ◽  
P. Matsudaira ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Binding Proteins ◽  
Actin Binding ◽  
Eukaryotic Cells ◽  
Dimensional Structure ◽  
Structural Basis ◽  
Actin Bundle ◽  
Actin Bundles ◽  
3 Dimensional ◽  
Macromolecular Assembly

Actin is a protein found in all eukaryotic cells. In its polymerized form, the cells use it for motility, cytokinesis and for cytoskeletal support. An example of this latter class is the actin bundle in the acrosomal process from the Limulus sperm. The different functions actin performs seem to arise from its interaction with the actin binding proteins. A 3-dimensional structure of this macromolecular assembly is essential to provide a structural basis for understanding this interaction in relationship to its development and functions.

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