Comprehensive assessment of chamber-specific and transmural heterogeneity in myofilament protein phosphorylation by top-down mass spectrometry.
The heart is characterized by a remarkable degree of heterogeneity, the basis of which is a subject of active investigation. Myofilament protein post-translational modifications (PTMs) represent a critical mechanism regulating cardiac contractility, and emerging evidence shows that pathological cardiac conditions induce contractile heterogeneity that correlates with transmural variations in the modification status of myofilament proteins. Nevertheless, whether there exists basal heterogeneity in myofilament protein PTMs in the heart remains unclear. Here we have systematically assessed chamber-specific and transmural variations in myofilament protein PTMs, specifically, the phosphorylation of cardiac troponin I (cTnI), cardiac troponin T (cTnT), tropomyosin (Tpm), and myosin light chain 2 (MLC2). We show that the phosphorylation of cTnI and αTm vary in the different chambers of the heart, whereas the phosphorylation of MLC2 and cTnT does not. In contrast, no significant transmural differences were observed in the phosphorylation of any of the myofilament proteins analyzed. These results highlight the importance of appropriate tissue sampling-particularly for studies aimed at elucidating disease mechanisms and biomarker discovery-in order to minimize potential variations arising from basal heterogeneity in myofilament PTMs in the heart.
Molecular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Zachery R
ZR
Gregorich
Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Ying
Y
Peng
Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA; Cellular and Molecular Pathology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA.
Nicole M
NM
Lane
Bruker Daltonics, Billerica, MA 01821, USA.
Jeremy J
JJ
Wolff
Department of Biostatistics & Medical Informatics, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Statistics, University of Wisconsin-Madison, Madison, WI 53706, USA.
Sijian
S
Wang
Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Wei
W
Guo
Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA; Human Proteomics Program, University of Wisconsin-Madison, Madison, WI 53706, USA.
Huseyin
H
Guner
Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Justin
J
Doop
Department of Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA.
Timothy A
TA
Hacker
Molecular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA; Cellular and Molecular Pathology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA; Human Proteomics Program, University of Wisconsin-Madison, Madison, WI 53706, USA. Electronic address: ge2@wisc.edu.
Ying
Y
Ge
D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D024722:Cardiac Myosins / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D009206:Myocardium / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism*; D018994:Myosin Light Chains / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D013552:Swine; D014335:Tropomyosin / Q000378:metabolism*; D019210:Troponin I / Q000378:metabolism*; D020107:Troponin T / Q000378:metabolism*
D018994:Myosin Light Chains; D014335:Tropomyosin; D019210:Troponin I; D020107:Troponin T; C107184:myosin light chain 2; D024722:Cardiac Myosins
Chamber heterogeneity; Mass spectrometry; Myofilament; Phosphorylation; Transmural heterogeneity