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Gelsolin deficiency blocks podosome assembly and produces increased bone mass and strength.

Chellaiah M, Kizer N, Silva M, Alvarez U, Kwiatkowski D, Hruska KA - J. Cell Biol. (2000)

Bottom Line: They failed to respond to the autocrine factor, OP, with stimulation of motility and bone resorption.Gelsolin deficiency was associated with normal skeletal development and endochondral bone growth.These observations demonstrate the critical role of gelsolin in podosome assembly, rapid cell movements, and signal transduction through the alpha(v)beta(3) integrin.

View Article: PubMed Central - PubMed

Affiliation: Renal Division, Department of Medicine, Barnes-Jewish Hospital, Washington University, St. Louis, Missouri 63110, USA.

ABSTRACT
Osteoclasts are unique cells that utilize podosomes instead of focal adhesions for matrix attachment and cytoskeletal remodeling during motility. We have shown that osteopontin (OP) binding to the alpha(v)beta(3) integrin of osteoclast podosomes stimulated cytoskeletal reorganization and bone resorption by activating a heteromultimeric signaling complex that includes gelsolin, pp(60c-src), and phosphatidylinositol 3'-kinase. Here we demonstrate that gelsolin deficiency blocks podosome assembly and alpha(v)beta(3)-stimulated signaling related to motility in gelsolin- mice. Gelsolin-deficient osteoclasts were hypomotile due to retarded remodeling of the actin cytoskeleton. They failed to respond to the autocrine factor, OP, with stimulation of motility and bone resorption. Gelsolin deficiency was associated with normal skeletal development and endochondral bone growth. However, gelsolin- mice had mildly abnormal epiphyseal structure, retained cartilage proteoglycans in metaphyseal trabeculae, and increased trabecular thickness. With age, the gelsolin-deficient mice expressed increased trabecular and cortical bone thickness producing mechanically stronger bones. These observations demonstrate the critical role of gelsolin in podosome assembly, rapid cell movements, and signal transduction through the alpha(v)beta(3) integrin.

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Polarization of the osteoclast plasma membrane as detected by distribution of the vacuolar H+ ATPase. (A) Confocal microscopy of an osteoclast derived from Gsn−/− cells. The section was taken at the level of the dentine slice as shown by the reflected light (red). The arrows point to areas of concentration of the H+ ATPase detected by the E11 antibody. (B) The areas of H+ ATPase concentration overlie a multiocular resorption pit produced by the osteoclast.
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Figure 8: Polarization of the osteoclast plasma membrane as detected by distribution of the vacuolar H+ ATPase. (A) Confocal microscopy of an osteoclast derived from Gsn−/− cells. The section was taken at the level of the dentine slice as shown by the reflected light (red). The arrows point to areas of concentration of the H+ ATPase detected by the E11 antibody. (B) The areas of H+ ATPase concentration overlie a multiocular resorption pit produced by the osteoclast.

Mentions: Bone resorption appears to proceed by the intricate coordination of several processes, including attachment, polarized secretion of acid and proteases, and active motility of osteoclasts along the bone surface (Kanehisa and Heersche 1988; Blair et al. 1989; Zambonin-Zallone et al. 1989). Even though osteoclasts isolated from Gsn−/− mice attach and spread well on glass coverslips and bone, the polarization efficiency was measured by immunostaining the osteoclasts with an antibody to the H+ ATPase proton pump responsible for mineral dissolution (Hemken et al. 1992). Osteoclasts derived from Gsn−/− cells were cultured on dentine slices, and the H+ ATPase, which is found in the ruffled border overlying resorption pits, was found to be concentrated at this location (Fig. 8). This indicates that signals for the osteoclasts to polarize are normal. Secondly, we analyzed the number and size of resorption pits produced in the basal conditions (PBS). The number of resorption pits was similar between Gsn+/+ and Gsn−/− mouse osteoclasts (Fig. 9 A). Compilation of pit area (XY) and pit depth (XZ) using confocal microscopy scans (Fig. 9 B) on multiple dentine slices with osteoclasts from multiple preparations (Table ) revealed competency of the Gsn−/− cells in basal conditions. However, response of Gsn−/− osteoclasts to OP treatment was absent, whereas pit complexity, pit area, and pit depth were increased in Gsn+/+ osteoclasts (Fig. 9 A and Table ). Since OP is a chemotactic factor, bone resorption in vivo probably proceeds under the influence of this factor regulating the direction of osteoclast motility. Thus, the lack of response to OP may reflect a diminished capacity for bone resorption in vivo.


Gelsolin deficiency blocks podosome assembly and produces increased bone mass and strength.

Chellaiah M, Kizer N, Silva M, Alvarez U, Kwiatkowski D, Hruska KA - J. Cell Biol. (2000)

Polarization of the osteoclast plasma membrane as detected by distribution of the vacuolar H+ ATPase. (A) Confocal microscopy of an osteoclast derived from Gsn−/− cells. The section was taken at the level of the dentine slice as shown by the reflected light (red). The arrows point to areas of concentration of the H+ ATPase detected by the E11 antibody. (B) The areas of H+ ATPase concentration overlie a multiocular resorption pit produced by the osteoclast.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169374&req=5

Figure 8: Polarization of the osteoclast plasma membrane as detected by distribution of the vacuolar H+ ATPase. (A) Confocal microscopy of an osteoclast derived from Gsn−/− cells. The section was taken at the level of the dentine slice as shown by the reflected light (red). The arrows point to areas of concentration of the H+ ATPase detected by the E11 antibody. (B) The areas of H+ ATPase concentration overlie a multiocular resorption pit produced by the osteoclast.
Mentions: Bone resorption appears to proceed by the intricate coordination of several processes, including attachment, polarized secretion of acid and proteases, and active motility of osteoclasts along the bone surface (Kanehisa and Heersche 1988; Blair et al. 1989; Zambonin-Zallone et al. 1989). Even though osteoclasts isolated from Gsn−/− mice attach and spread well on glass coverslips and bone, the polarization efficiency was measured by immunostaining the osteoclasts with an antibody to the H+ ATPase proton pump responsible for mineral dissolution (Hemken et al. 1992). Osteoclasts derived from Gsn−/− cells were cultured on dentine slices, and the H+ ATPase, which is found in the ruffled border overlying resorption pits, was found to be concentrated at this location (Fig. 8). This indicates that signals for the osteoclasts to polarize are normal. Secondly, we analyzed the number and size of resorption pits produced in the basal conditions (PBS). The number of resorption pits was similar between Gsn+/+ and Gsn−/− mouse osteoclasts (Fig. 9 A). Compilation of pit area (XY) and pit depth (XZ) using confocal microscopy scans (Fig. 9 B) on multiple dentine slices with osteoclasts from multiple preparations (Table ) revealed competency of the Gsn−/− cells in basal conditions. However, response of Gsn−/− osteoclasts to OP treatment was absent, whereas pit complexity, pit area, and pit depth were increased in Gsn+/+ osteoclasts (Fig. 9 A and Table ). Since OP is a chemotactic factor, bone resorption in vivo probably proceeds under the influence of this factor regulating the direction of osteoclast motility. Thus, the lack of response to OP may reflect a diminished capacity for bone resorption in vivo.

Bottom Line: They failed to respond to the autocrine factor, OP, with stimulation of motility and bone resorption.Gelsolin deficiency was associated with normal skeletal development and endochondral bone growth.These observations demonstrate the critical role of gelsolin in podosome assembly, rapid cell movements, and signal transduction through the alpha(v)beta(3) integrin.

View Article: PubMed Central - PubMed

Affiliation: Renal Division, Department of Medicine, Barnes-Jewish Hospital, Washington University, St. Louis, Missouri 63110, USA.

ABSTRACT
Osteoclasts are unique cells that utilize podosomes instead of focal adhesions for matrix attachment and cytoskeletal remodeling during motility. We have shown that osteopontin (OP) binding to the alpha(v)beta(3) integrin of osteoclast podosomes stimulated cytoskeletal reorganization and bone resorption by activating a heteromultimeric signaling complex that includes gelsolin, pp(60c-src), and phosphatidylinositol 3'-kinase. Here we demonstrate that gelsolin deficiency blocks podosome assembly and alpha(v)beta(3)-stimulated signaling related to motility in gelsolin- mice. Gelsolin-deficient osteoclasts were hypomotile due to retarded remodeling of the actin cytoskeleton. They failed to respond to the autocrine factor, OP, with stimulation of motility and bone resorption. Gelsolin deficiency was associated with normal skeletal development and endochondral bone growth. However, gelsolin- mice had mildly abnormal epiphyseal structure, retained cartilage proteoglycans in metaphyseal trabeculae, and increased trabecular thickness. With age, the gelsolin-deficient mice expressed increased trabecular and cortical bone thickness producing mechanically stronger bones. These observations demonstrate the critical role of gelsolin in podosome assembly, rapid cell movements, and signal transduction through the alpha(v)beta(3) integrin.

Show MeSH
Related in: MedlinePlus