Runx2 regulates G protein-coupled signaling pathways to control growth of osteoblast progenitors.
Runt-related transcription factor 2 (Runx2) controls lineage commitment, proliferation, and anabolic functions of osteoblasts as the subnuclear effector of multiple signaling axes (e.g. transforming growth factor-beta/BMP-SMAD, SRC/YES-YAP, and GROUCHO/TLE). Runx2 levels oscillate during the osteoblast cell cycle with maximal levels in G(1). Here we examined what functions and target genes of Runx2 control osteoblast growth. Forced expression of wild type Runx2 suppresses growth of Runx2(-/-) osteoprogenitors. Point mutants defective for binding to WW domain or SMAD proteins or the nuclear matrix retain this growth regulatory ability. Hence, key signaling pathways are dispensable for growth control by Runx2. However, mutants defective for DNA binding or C-terminal gene repression/activation functions do not block proliferation. Target gene analysis by Affymetrix expression profiling shows that the C terminus of Runx2 regulates genes involved in G protein-coupled receptor signaling (e.g. Rgs2, Rgs4, Rgs5, Rgs16, Gpr23, Gpr30, Gpr54, Gpr64, and Gna13). We further examined the function of two genes linked to cAMP signaling as follows: Gpr30 that is stimulated and Rgs2 that is down-regulated by Runx2. RNA interference of Gpr30 and forced expression of Rgs2 in each case inhibit osteoblast proliferation. Notwithstanding its growth-suppressive potential, our results surprisingly indicate that Runx2 may sensitize cAMP-related G protein-coupled receptor signaling by activating Gpr30 and repressing Rgs2 gene expression in osteoblasts to increase responsiveness to mitogenic signals.
Teplyuk
Nadiya M
NM
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
Galindo
Mario
M
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
Teplyuk
Viktor I
VI
Bioinformatics Core, Program in Molecular Medicine, Worcester, Massachusetts 01655.
Pratap
Jitesh
J
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
Young
Daniel W
DW
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
Lapointe
David
D
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655; Information Services, University of Massachusetts Medical School, Worcester, Massachusetts 01655.
Javed
Amjad
A
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
Stein
Janet L
JL
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
Lian
Jane B
JB
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
Stein
Gary S
GS
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655.
van Wijnen
Andre J
AJ
Department of Cell Biology and Cancer Center, Worcester, Massachusetts 01655. Electronic address: andre.vanwijnen@umassmed.edu.
D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D002453:Cell Cycle / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002461:Cell Line, Transformed; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*
D050659:Core Binding Factor Alpha 1 Subunit; D043562:Receptors, G-Protein-Coupled; C493716:Runx2 protein, mouse