Limits...
The Golgi-associated hook3 protein is a member of a novel family of microtubule-binding proteins.

Walenta JH, Didier AJ, Liu X, Krämer H - J. Cell Biol. (2001)

Bottom Line: Microtubules are central to the spatial organization of diverse membrane-trafficking systems.Human Hook3 bound to Golgi membranes in vitro and was enriched in the cis-Golgi in vivo.Unlike other cis-Golgi-associated proteins, however, a large fraction of Hook3 maintained its juxtanuclear localization after Brefeldin A treatment, indicating a Golgi-independent mechanism for Hook3 localization.

View Article: PubMed Central - PubMed

Affiliation: Center for Basic Neuroscience and Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.

ABSTRACT
Microtubules are central to the spatial organization of diverse membrane-trafficking systems. Here, we report that Hook proteins constitute a novel family of cytosolic coiled coil proteins that bind to organelles and to microtubules. The conserved NH(2)-terminal domains of Hook proteins mediate attachment to microtubules, whereas the more divergent COOH-terminal domains mediate the binding to organelles. Human Hook3 bound to Golgi membranes in vitro and was enriched in the cis-Golgi in vivo. Unlike other cis-Golgi-associated proteins, however, a large fraction of Hook3 maintained its juxtanuclear localization after Brefeldin A treatment, indicating a Golgi-independent mechanism for Hook3 localization. Because overexpression of Hook3 caused fragmentation of the Golgi complex, we propose that Hook3 participates in defining the architecture and localization of the mammalian Golgi complex.

Show MeSH

Related in: MedlinePlus

Juxtanuclear localization of hHK3 after BfA treatment. Localization of endogenous Hook3 in Vero (A–L) and HeLa cells (M–O) was compared with that of β-COP (B and N), TGN46 (E), and GM130 (H and K), after treatment with BfA (10 μg/ml) for 1 h (A–I) or BfA (10 μg/ml) for 1 h, and then BfA and NZ (10 μg/ml) for 1 h (J–L) or NZ (10 μg/ml) alone for 1 h (M–O). After 1 h of BfA treatment, β-COP protein was cytosolic (B), but the majority of hHk3 protein remained in a juxtanuclear position (A, D, and G). In BfA-treated cells, a fraction of hHK3 protein colocalized with the cis-Golgi matrix protein GM130 in distinct punctae (G–I, arrows). The majority of hHK3 protein was released from its juxtanuclear position after NZ was added to the BfA-treated cells; then, the majority of hHK3 localized to the GM130-positive punctae (J–L, arrows). After NZ treatment of HeLa cells, hHK3 (M) was associated with the resultant Golgi fragments (arrowheads), which were identified by β-COP labeling (N). In the merged images, hHK3 is visualized in red; and Golgi markers, in green.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2198811&req=5

Figure 5: Juxtanuclear localization of hHK3 after BfA treatment. Localization of endogenous Hook3 in Vero (A–L) and HeLa cells (M–O) was compared with that of β-COP (B and N), TGN46 (E), and GM130 (H and K), after treatment with BfA (10 μg/ml) for 1 h (A–I) or BfA (10 μg/ml) for 1 h, and then BfA and NZ (10 μg/ml) for 1 h (J–L) or NZ (10 μg/ml) alone for 1 h (M–O). After 1 h of BfA treatment, β-COP protein was cytosolic (B), but the majority of hHk3 protein remained in a juxtanuclear position (A, D, and G). In BfA-treated cells, a fraction of hHK3 protein colocalized with the cis-Golgi matrix protein GM130 in distinct punctae (G–I, arrows). The majority of hHK3 protein was released from its juxtanuclear position after NZ was added to the BfA-treated cells; then, the majority of hHK3 localized to the GM130-positive punctae (J–L, arrows). After NZ treatment of HeLa cells, hHK3 (M) was associated with the resultant Golgi fragments (arrowheads), which were identified by β-COP labeling (N). In the merged images, hHK3 is visualized in red; and Golgi markers, in green.

Mentions: The drugs BfA and NZ were used to further probe the properties of hHK3. Treatment with BfA results in the release of β-COP proteins into the cytosol (Fig. 5 B) and the disruption of the Golgi complex (for review see Chardin and McCormick 1999). The strongest staining for hHK3, however, remained in a juxtanuclear accumulation even after a 1-h treatment with 10 μg/ml BfA (Fig. 5, A–I). Under these conditions, the cis-Golgi matrix protein GM130, localizes to dispersed punctate structures (Fig. 5 H; Nakamura et al. 1995; Seemann et al. 2000). A significant fraction of hHK3 labeling in BfA-treated cells colocalized with these GM130-positive punctae (Fig. 5, G–I, arrows).


The Golgi-associated hook3 protein is a member of a novel family of microtubule-binding proteins.

Walenta JH, Didier AJ, Liu X, Krämer H - J. Cell Biol. (2001)

Juxtanuclear localization of hHK3 after BfA treatment. Localization of endogenous Hook3 in Vero (A–L) and HeLa cells (M–O) was compared with that of β-COP (B and N), TGN46 (E), and GM130 (H and K), after treatment with BfA (10 μg/ml) for 1 h (A–I) or BfA (10 μg/ml) for 1 h, and then BfA and NZ (10 μg/ml) for 1 h (J–L) or NZ (10 μg/ml) alone for 1 h (M–O). After 1 h of BfA treatment, β-COP protein was cytosolic (B), but the majority of hHk3 protein remained in a juxtanuclear position (A, D, and G). In BfA-treated cells, a fraction of hHK3 protein colocalized with the cis-Golgi matrix protein GM130 in distinct punctae (G–I, arrows). The majority of hHK3 protein was released from its juxtanuclear position after NZ was added to the BfA-treated cells; then, the majority of hHK3 localized to the GM130-positive punctae (J–L, arrows). After NZ treatment of HeLa cells, hHK3 (M) was associated with the resultant Golgi fragments (arrowheads), which were identified by β-COP labeling (N). In the merged images, hHK3 is visualized in red; and Golgi markers, in green.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2198811&req=5

Figure 5: Juxtanuclear localization of hHK3 after BfA treatment. Localization of endogenous Hook3 in Vero (A–L) and HeLa cells (M–O) was compared with that of β-COP (B and N), TGN46 (E), and GM130 (H and K), after treatment with BfA (10 μg/ml) for 1 h (A–I) or BfA (10 μg/ml) for 1 h, and then BfA and NZ (10 μg/ml) for 1 h (J–L) or NZ (10 μg/ml) alone for 1 h (M–O). After 1 h of BfA treatment, β-COP protein was cytosolic (B), but the majority of hHk3 protein remained in a juxtanuclear position (A, D, and G). In BfA-treated cells, a fraction of hHK3 protein colocalized with the cis-Golgi matrix protein GM130 in distinct punctae (G–I, arrows). The majority of hHK3 protein was released from its juxtanuclear position after NZ was added to the BfA-treated cells; then, the majority of hHK3 localized to the GM130-positive punctae (J–L, arrows). After NZ treatment of HeLa cells, hHK3 (M) was associated with the resultant Golgi fragments (arrowheads), which were identified by β-COP labeling (N). In the merged images, hHK3 is visualized in red; and Golgi markers, in green.
Mentions: The drugs BfA and NZ were used to further probe the properties of hHK3. Treatment with BfA results in the release of β-COP proteins into the cytosol (Fig. 5 B) and the disruption of the Golgi complex (for review see Chardin and McCormick 1999). The strongest staining for hHK3, however, remained in a juxtanuclear accumulation even after a 1-h treatment with 10 μg/ml BfA (Fig. 5, A–I). Under these conditions, the cis-Golgi matrix protein GM130, localizes to dispersed punctate structures (Fig. 5 H; Nakamura et al. 1995; Seemann et al. 2000). A significant fraction of hHK3 labeling in BfA-treated cells colocalized with these GM130-positive punctae (Fig. 5, G–I, arrows).

Bottom Line: Microtubules are central to the spatial organization of diverse membrane-trafficking systems.Human Hook3 bound to Golgi membranes in vitro and was enriched in the cis-Golgi in vivo.Unlike other cis-Golgi-associated proteins, however, a large fraction of Hook3 maintained its juxtanuclear localization after Brefeldin A treatment, indicating a Golgi-independent mechanism for Hook3 localization.

View Article: PubMed Central - PubMed

Affiliation: Center for Basic Neuroscience and Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.

ABSTRACT
Microtubules are central to the spatial organization of diverse membrane-trafficking systems. Here, we report that Hook proteins constitute a novel family of cytosolic coiled coil proteins that bind to organelles and to microtubules. The conserved NH(2)-terminal domains of Hook proteins mediate attachment to microtubules, whereas the more divergent COOH-terminal domains mediate the binding to organelles. Human Hook3 bound to Golgi membranes in vitro and was enriched in the cis-Golgi in vivo. Unlike other cis-Golgi-associated proteins, however, a large fraction of Hook3 maintained its juxtanuclear localization after Brefeldin A treatment, indicating a Golgi-independent mechanism for Hook3 localization. Because overexpression of Hook3 caused fragmentation of the Golgi complex, we propose that Hook3 participates in defining the architecture and localization of the mammalian Golgi complex.

Show MeSH
Related in: MedlinePlus