Alexander Pfeifer

Bodo Haas

Darren E Casteel

Gerry Boss

Hema Rangaswami

Nisha Marathe

Raphaela Schwappacher

Renate B Pilz

Sanford Shattil

BMC Pharmacology

PubMed

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ORAL PRESENTATION Open Access
Src activation by cGMP/PKG II in osteoblasts:
characterization of a mechano-sensitive signalling
complex
Hema Rangaswami1, Raphaela Schwappacher1, Nisha Marathe1, Darren E Casteel1, Bodo Haas2, Alexander Pfeifer2,
Sanford Shattil1, Gerry Boss1, Renate B Pilz1*
From 5th International Conference on cGMP: Generators, Effectors and Therapeutic Implications
Halle, Germany. 24-26 June 2011
Background
Mechanical stimulation of bone cells is critical for main-
taining bone mass and strength, and a better understand-
ing of how mechanical stimuli are converted into
intracellular signals to activate an anabolic program in
osteoblasts/cytes is fundamental to improving treatments
for osteo-degenerative diseases [1,2]. Weight bearing and
locomotion stimulate interstitial fluid flow through the
bone canalicular system, and the resultant shear stress is
thought to be a major mechanism whereby mechanical
forces stimulate osteoblast/osteocyte growth and differ-
entiation [1,2]. In primary osteoblasts and osteoblast/
cyte-like cell lines, fluid shear stress induces rapid expres-
sion of c-fos, fra-1, fra-2, and fosB/ΔfosB mRNAs [3];
these genes encode transcriptional regulators important
for osteoblast proliferation and differentiation, as demon-
strated by the phenotypes of mice that over-express or
lack these proteins, respectively [4]. We have previously
shown that fluid shear stress increases osteoblast/cyte
nitric oxide (NO) production, leading to increased cGMP
synthesis and activation of cGMP-dependent protein
kinases (PKGs). The NO/cGMP/PKG signaling pathway
is required for shear-induced expression of all four fos
family genes, and induction of these genes is mediated
through activation of the mitogen-activated protein
kinases Erk1/2 [3]. However, molecular mechanisms
leading to Erk activation in shear-stressed osteoblasts are
largely unknown.
Results
We have now defined the events leading from shear stress
activation of NO/cGMP/PKG II to the activation of Src
[5]; we show that this pathway is required for Erk activa-
tion, and controls osteoblast proliferation and survival. We
found a novel link between NO/cGMP/PKG and b3 integ-
rins, the key mechano-sensors in bone, and show that
PKG II activates b3-associated Src by activating the tyro-
sine phosphatase Shp-1. PKG II directly phosphorylates
and stimulates Shp-1 activity, which de-phosphorylates a
C-terminal, inhibitory phosphorylation site on Src, leading
to Src activation. Fluid shear stress triggers PKG II, Src,
and Shp-1/2 recruitment to a mechano-sensitive complex
containing b3 integrins, defining a novel “mechanosome”.
We found that PKG II-null mice have defective osteoblast
Src/Erk signaling, decreased Erk-dependent gene expres-
sion in bone, and impaired osteoblast-dependent, mem-
branous bone formation. These results complement
previous studies in PKG II-deficient mice, which showed
defective chondroblast differentiation and endochondral
bone formation, and studies in NO synthase-deficient
mice, which demonstrated an important role of NO in
osteoblast biology [6,7].
Conclusion
Our findings reveal crosstalk between NO/cGMP/PKG
and integrins, establish a new mechanism of Src activation,
and fill a gap in our understanding of how mechanical
forces acting on cell-matrix adhesions are translated into
cellular responses. Since Src controls Erk, a key regulator
of osteoblast growth and survival, our results support
using PKG-activating drugs as mechano-mimetics for
treating osteoporosis.
* Correspondence: rpilz@ucsd.edu
1Department of Medicine, University of California at San Diego, La Jolla, CA
92093, USA
Full list of author information is available at the end of the article
Rangaswami et al. BMC Pharmacology 2011, 11(Suppl 1):O24
http://www.biomedcentral.com/1471-2210/11/S1/O24
© 2011 Rangaswami et al; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Author details
1Department of Medicine, University of California at San Diego, La Jolla, CA
92093, USA. 2Institute for Pharmacology and Biomedical Center, University of
Bonn, 53105 Bonn, Germany.
Published: 1 August 2011
References
1. Ehrlich PJ, Lanyon LE: Mechanical strain and bone cell function: a review.
Osteoporos. Int 2002, 13:688-700.
2. Ozcivici E, Luu YK, Adler B, Qin YX, Rubin J, Judex S, Rubin CT: Mechanical
signals as anabolic agents in bone. Nat Rev Rheumatol 2010, 6:50-59.
3. Rangaswami H, Marathe N, Zhuang S, Chen Y, Yeh JC, Frangos JA, Boss GR,
Pilz RB: Type II cGMP-dependent protein kinase mediates osteoblast
mechanotransduction. J Biol Chem 2009, 284:14796-14808.
4. Wagner EF, Eferl R: Fos/AP-1 proteins in bone and the immune system.
Immunol Rev 2005, 208:126-140.
5. Rangaswami H, Schwappacher R, Marathe N, Zhuang S, Casteel DE, Haas B,
Chen Y, Pfeifer A, Kato H, Shattil S, Boss GB, Pilz RB: Cyclic GMP and
protein kinase G control a Src-containing mechanosome in osteoblasts.
Sci Signal 2010, 3:ra91.
6. Pfeifer A, Aszòdi A, Seidler U, Ruth P, Hofmann F, Fässler R: Intestinal
secretory defects and dwarfism in mice lacking cGMP-dependent
protein kinase II. Science 1996, 274:2082-2086.
7. Armour KE, Armour KJ, Gallagher ME, Godecke A, Helfrich MH, Reid DM,
Ralston SH: Defective bone formation and anabolic response to
exogenous estrogen in mice with targeted disruption of endothelial
nitric oxide synthase. Endocrinology 2001, 142:760-766.
doi:10.1186/1471-2210-11-S1-O24
Cite this article as: Rangaswami et al.: Src activation by cGMP/PKG II in
osteoblasts: characterization of a mechano-sensitive signalling complex.
BMC Pharmacology 2011 11(Suppl 1):O24.
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Page 2 of 2


Src activation by cGMP/PKG II in osteoblasts: characterization of a mechano-sensitive signalling complex

CT: Mechanical signals as anabolic agents in bone. Nat Rev Rheumatol

Eferl R: Fos/AP-1 proteins in bone and the immune system. Immunol Rev

Fässler R: Intestinal secretory defects and dwarfism in mice lacking cGMP-dependent protein kinase II.

Lanyon LE: Mechanical strain and bone cell function: a review. Osteoporos. Int

RB: Cyclic GMP and protein kinase G control a Src-containing mechanosome in osteoblasts. Sci Signal

RB: Type II cGMP-dependent protein kinase mediates osteoblast mechanotransduction.

SH: Defective bone formation and anabolic response to exogenous estrogen in mice with targeted disruption of endothelial nitric oxide synthase. Endocrinology

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Src activation by cGMP/PKG II in osteoblasts: characterization of a mechano-sensitive signalling complex

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