Limits...
Mammalian Abp1, a signal-responsive F-actin-binding protein, links the actin cytoskeleton to endocytosis via the GTPase dynamin.

Kessels MM, Engqvist-Goldstein AE, Drubin DG, Qualmann B - J. Cell Biol. (2001)

Bottom Line: While overexpression of Abp1's actin-binding modules did not interfere with endocytosis, overexpression of the SH3 domain led to a potent block of transferrin uptake.The endocytosis block was rescued by cooverexpression of dynamin.Since the addition of the actin-binding modules of Abp1 to the SH3 domain construct also fully restored endocytosis, Abp1 may support endocytosis by combining its SH3 domain interactions with cytoskeletal functions in response to signaling cascades converging on this linker protein.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, D-39008 Magdeburg, Germany. kessels@ifn-magdeburg.de

ABSTRACT
The actin cytoskeleton has been implicated in endocytosis, yet few molecular links to the endocytic machinery have been established. Here we show that the mammalian F-actin-binding protein Abp1 (SH3P7/HIP-55) can functionally link the actin cytoskeleton to dynamin, a GTPase that functions in endocytosis. Abp1 binds directly to dynamin in vitro through its SH3 domain. Coimmunoprecipitation and colocalization studies demonstrated the in vivo relevance of this interaction. In neurons, mammalian Abp1 and dynamin colocalized at actin-rich sites proximal to the cell body during synaptogenesis. In fibroblasts, mAbp1 appeared at dynamin-rich sites of endocytosis upon growth factor stimulation. To test whether Abp1 functions in endocytosis, we overexpressed several Abp1 constructs in Cos-7 cells and assayed receptor-mediated endocytosis. While overexpression of Abp1's actin-binding modules did not interfere with endocytosis, overexpression of the SH3 domain led to a potent block of transferrin uptake. This implicates the Abp1/dynamin interaction in endocytic function. The endocytosis block was rescued by cooverexpression of dynamin. Since the addition of the actin-binding modules of Abp1 to the SH3 domain construct also fully restored endocytosis, Abp1 may support endocytosis by combining its SH3 domain interactions with cytoskeletal functions in response to signaling cascades converging on this linker protein.

Show MeSH
Schematic representation of Abp1 function at the interface of endocytosis and actin cytoskeleton.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2169459&req=5

Figure 10: Schematic representation of Abp1 function at the interface of endocytosis and actin cytoskeleton.

Mentions: Here we have shown that the SH3 domain of mammalian Abp1 interacts with dynamin in vitro and in vivo. Overexpression of the Abp1 SH3 domain blocks endocytosis in Cos-7 cells (Fig. 5). Overexpression of other SH3 domains that bind to dynamin (i.e., those of amphiphysins and syndapins) led to similar inhibition of receptor-mediated endocytosis (Wigge et al. 1997; Qualmann and Kelly 2000). We were able to demonstrate that the impairment of endocytosis caused by the SH3 domain of Abp1 is dependent on interaction with dynamin, while the more moderate effect of the flexible Src kinase target domain is not. The fact that the SH3 domain overexpression phenotype was completely suppressed by dynamin cooverexpression strongly implicates Abp1 in dynamin functions. Our analyses furthermore suggest that Abp1 may serve both as a functional and physical link between receptor-mediated endocytosis and the actin cytoskeleton and that, besides Abp1's dynamin-binding SH3 domain, both of Abp1's actin-binding modules seem to be involved in this function (Fig. 10).


Mammalian Abp1, a signal-responsive F-actin-binding protein, links the actin cytoskeleton to endocytosis via the GTPase dynamin.

Kessels MM, Engqvist-Goldstein AE, Drubin DG, Qualmann B - J. Cell Biol. (2001)

Schematic representation of Abp1 function at the interface of endocytosis and actin cytoskeleton.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169459&req=5

Figure 10: Schematic representation of Abp1 function at the interface of endocytosis and actin cytoskeleton.
Mentions: Here we have shown that the SH3 domain of mammalian Abp1 interacts with dynamin in vitro and in vivo. Overexpression of the Abp1 SH3 domain blocks endocytosis in Cos-7 cells (Fig. 5). Overexpression of other SH3 domains that bind to dynamin (i.e., those of amphiphysins and syndapins) led to similar inhibition of receptor-mediated endocytosis (Wigge et al. 1997; Qualmann and Kelly 2000). We were able to demonstrate that the impairment of endocytosis caused by the SH3 domain of Abp1 is dependent on interaction with dynamin, while the more moderate effect of the flexible Src kinase target domain is not. The fact that the SH3 domain overexpression phenotype was completely suppressed by dynamin cooverexpression strongly implicates Abp1 in dynamin functions. Our analyses furthermore suggest that Abp1 may serve both as a functional and physical link between receptor-mediated endocytosis and the actin cytoskeleton and that, besides Abp1's dynamin-binding SH3 domain, both of Abp1's actin-binding modules seem to be involved in this function (Fig. 10).

Bottom Line: While overexpression of Abp1's actin-binding modules did not interfere with endocytosis, overexpression of the SH3 domain led to a potent block of transferrin uptake.The endocytosis block was rescued by cooverexpression of dynamin.Since the addition of the actin-binding modules of Abp1 to the SH3 domain construct also fully restored endocytosis, Abp1 may support endocytosis by combining its SH3 domain interactions with cytoskeletal functions in response to signaling cascades converging on this linker protein.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, D-39008 Magdeburg, Germany. kessels@ifn-magdeburg.de

ABSTRACT
The actin cytoskeleton has been implicated in endocytosis, yet few molecular links to the endocytic machinery have been established. Here we show that the mammalian F-actin-binding protein Abp1 (SH3P7/HIP-55) can functionally link the actin cytoskeleton to dynamin, a GTPase that functions in endocytosis. Abp1 binds directly to dynamin in vitro through its SH3 domain. Coimmunoprecipitation and colocalization studies demonstrated the in vivo relevance of this interaction. In neurons, mammalian Abp1 and dynamin colocalized at actin-rich sites proximal to the cell body during synaptogenesis. In fibroblasts, mAbp1 appeared at dynamin-rich sites of endocytosis upon growth factor stimulation. To test whether Abp1 functions in endocytosis, we overexpressed several Abp1 constructs in Cos-7 cells and assayed receptor-mediated endocytosis. While overexpression of Abp1's actin-binding modules did not interfere with endocytosis, overexpression of the SH3 domain led to a potent block of transferrin uptake. This implicates the Abp1/dynamin interaction in endocytic function. The endocytosis block was rescued by cooverexpression of dynamin. Since the addition of the actin-binding modules of Abp1 to the SH3 domain construct also fully restored endocytosis, Abp1 may support endocytosis by combining its SH3 domain interactions with cytoskeletal functions in response to signaling cascades converging on this linker protein.

Show MeSH