TY - JOUR
T1 - Myosin phosphatase modulates the cardiac cell fate by regulating the subcellular localization of Nkx2.5 in a Wnt/rho-associated protein kinase-dependent pathway
AU - Ryan, Tammy
AU - Shelton, Michael
AU - Lambert, Jean Philippe
AU - Malecova, Barbora
AU - Boisvenue, Sophie
AU - Ruel, Marc
AU - Figeys, Daniel
AU - Puri, Pier Lorenzo
AU - Skerjanc, Ilona S.
PY - 2013/1/18
Y1 - 2013/1/18
N2 - Rationale: Nkx2.5 is a transcription factor that regulates cardiomyogenesis in vivo and in embryonic stem cells. It is also a common target in congenital heart disease. Although Nkx2.5 has been implicated in the regulation of many cellular processes that ultimately contribute to cardiomyogenesis and morphogenesis of the mature heart, relatively little is known about how it is regulated at a functional level. Objective: We have undertaken a proteomic screen to identify novel binding partners of Nkx2.5 during cardiomyogenic differentiation in an effort to better understand the regulation of its transcriptional activity. Methods and Results: Purification of Nkx2.5 from differentiating cells identified the myosin phosphatase subunits protein phosphatase 1β and myosin phosphatase targeting subunit 1 (Mypt1) as novel binding partners. The interaction with protein phosphatase 1 β/Mypt1 resulted in exclusion of Nkx2.5 from the nucleus and, consequently, inhibition of its transcriptional activity. Exclusion of Nkx2.5 was inhibited by treatment with leptomycin B and was dependent on an Mypt1 nuclear export signal. Furthermore, in transient transfection experiments, Nkx2.5 colocalized outside the nucleus with phosphorylated Mypt1 in a manner dependent on Wnt signaling and Rho-associated protein kinase. Treatment of differentiating mouse embryonic stem cells with Wnt3a resulted in enhanced phosphorylation of endogenous Mypt1, increased nuclear exclusion of endogenous Nkx2.5, and a failure to undergo terminal cardiomyogenesis. Finally, knockdown of Mypt1 resulted in rescue of Wnt3a-mediated inhibition of cardiomyogenesis, indicating that Mypt1 is required for this process. Conclusions: We have identified a novel interaction between Nkx2.5 and myosin phosphatase. Promoting this interaction represents a novel mechanism whereby Wnt3a regulates Nkx2.5 and inhibits cardiomyogenesis.
AB - Rationale: Nkx2.5 is a transcription factor that regulates cardiomyogenesis in vivo and in embryonic stem cells. It is also a common target in congenital heart disease. Although Nkx2.5 has been implicated in the regulation of many cellular processes that ultimately contribute to cardiomyogenesis and morphogenesis of the mature heart, relatively little is known about how it is regulated at a functional level. Objective: We have undertaken a proteomic screen to identify novel binding partners of Nkx2.5 during cardiomyogenic differentiation in an effort to better understand the regulation of its transcriptional activity. Methods and Results: Purification of Nkx2.5 from differentiating cells identified the myosin phosphatase subunits protein phosphatase 1β and myosin phosphatase targeting subunit 1 (Mypt1) as novel binding partners. The interaction with protein phosphatase 1 β/Mypt1 resulted in exclusion of Nkx2.5 from the nucleus and, consequently, inhibition of its transcriptional activity. Exclusion of Nkx2.5 was inhibited by treatment with leptomycin B and was dependent on an Mypt1 nuclear export signal. Furthermore, in transient transfection experiments, Nkx2.5 colocalized outside the nucleus with phosphorylated Mypt1 in a manner dependent on Wnt signaling and Rho-associated protein kinase. Treatment of differentiating mouse embryonic stem cells with Wnt3a resulted in enhanced phosphorylation of endogenous Mypt1, increased nuclear exclusion of endogenous Nkx2.5, and a failure to undergo terminal cardiomyogenesis. Finally, knockdown of Mypt1 resulted in rescue of Wnt3a-mediated inhibition of cardiomyogenesis, indicating that Mypt1 is required for this process. Conclusions: We have identified a novel interaction between Nkx2.5 and myosin phosphatase. Promoting this interaction represents a novel mechanism whereby Wnt3a regulates Nkx2.5 and inhibits cardiomyogenesis.
KW - cardiac differentiation
KW - cardiac transcription factors
KW - differentiation
KW - embryonic stem cells
KW - gene regulation
KW - myogenesis
KW - signal transduction
KW - stem cells
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UR - http://www.scopus.com/inward/citedby.url?scp=84872842515&partnerID=8YFLogxK
U2 - 10.1161/CIRCRESAHA.112.275818
DO - 10.1161/CIRCRESAHA.112.275818
M3 - Article
C2 - 23168335
AN - SCOPUS:84872842515
VL - 112
SP - 257
EP - 266
JO - Circulation Research
JF - Circulation Research
SN - 0009-7330
IS - 2
ER -