Tyrosine phosphorylation modifies protein kinase C delta-dependent phosphorylation of cardiac troponin I.
Our study identifies tyrosine phosphorylation as a novel protein kinase Cdelta (PKCdelta) activation mechanism that modifies PKCdelta-dependent phosphorylation of cardiac troponin I (cTnI), a myofilament regulatory protein. PKCdelta phosphorylates cTnI at Ser23/Ser24 when activated by lipid cofactors; Src phosphorylates PKCdelta at Tyr311 and Tyr332 leading to enhanced PKCdelta autophosphorylation at Thr505 (its activation loop) and PKCdelta-dependent cTnI phosphorylation at both Ser23/Ser24 and Thr144. The Src-dependent acquisition of cTnI-Thr144 kinase activity is abrogated by Y311F or T505A substitutions. Treatment of detergent-extracted single cardiomyocytes with lipid-activated PKCdelta induces depressed tension at submaximum but not maximum [Ca2+] as expected for cTnI-Ser23/Ser24 phosphorylation. Treatment of myocytes with Src-activated PKCdelta leads to depressed maximum tension and cross-bridge kinetics, attributable to a dominant effect of cTnI-Thr144 phosphorylation. Our data implicate PKCdelta-Tyr311/Thr505 phosphorylation as dynamically regulated modifications that alter PKCdelta enzymology and allow for stimulus-specific control of cardiac mechanics during growth factor stimulation and oxidative stress.
Department of Internal Medicine, Cardiovascular Research Center, University of Kentucky, Lexington, Kentucky 40536, USA.
Marius P
MP
Sumandea
Vitalyi O
VO
Rybin
Aaron C
AC
Hinken
Chaojian
C
Wang
Tomoyoshi
T
Kobayashi
Erin
E
Harleton
Gail
G
Sievert
C William
CW
Balke
Steven J
SJ
Feinmark
R John
RJ
Solaro
Susan F
SF
Steinberg
D000818:Animals; D002478:Cells, Cultured; D017930:Genes, Reporter; D006352:Heart Ventricles / Q000378:metabolism; D008297:Male; D016296:Mutagenesis; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D019210:Troponin I / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
D011993:Recombinant Fusion Proteins; D019210:Troponin I; D019000:Phosphotyrosine; D014443:Tyrosine; D051745:Protein Kinase C-delta