Phosphoprotein abundance changes in hypertensive cardiac remodeling

Abstract

There is over-whelming evidence that protein phosphorylations regulate cardiac function and remodeling. A wide variety of protein kinases, e.g., phosphoinositide 3-kinase (PI3K), Akt, GSK-3, TGFβ, and PKA, MAPKs, PKC, Erks, and Jaks, as well as phosphatases, e.g., phosphatase I (PP1) and calcineurin, control cardiomyocyte growth and contractility. In the present work, we used global phosphoprotein profiling to identify phosphorylated proteins associated with pressure overload (PO) cardiac hypertrophy and heart failure. Phosphoproteins from hypertrophic and systolic failing hearts from male hypertensive Dahl salt-sensitive rats, trans-aortic banded (TAC), and spontaneously hypertensive heart failure (SHHF) rats were analyzed. Profiling was performed by 2-dimensional difference in gel electrophoresis (2D-DIGE) on phospho-enriched proteins. A total of 25 common phosphoproteins with differences in abundance in (1) the 3 hypertrophic and/or (2) the 2 systolic failure heart models were identified (CI>99%) by matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) and Mascot analysis. Among these were (1) myofilament proteins, including alpha-tropomyosin and myosin regulatory light chain 2, cap Z interacting protein (cap ZIP), and tubulin β5; (2) mitochondrial proteins, including pyruvate dehydrogenase α, branch chain ketoacid dehydrogenase E1, and mitochondrial creatine kinase; (3) phosphatases, including protein phosphatase 2A and protein phosphatase 1 regulatory subunit; and (4) other proteins including proteosome subunits α type 3 and β type 7, and eukaryotic translation initiation factor 1A (eIF1A). The results include previously described and novel phosphoproteins in cardiac hypertrophy and systolic failure.

Cardiac-specific deletion of protein phosphatase 1β promotes increased myofilament protein phosphorylation and contractile alterations

“…Hence, it is possible that phosphorylation status of other unrecognized proteins might contribute to the disease development in PP1β deficient mice or that other phosphorylation sites exist in MLC2V or cMyBPC that have unrecognized functions that are not strictly lusitropic [49]. For example, PP1β may dephosphorylate other potential cMyBPC phosphorylation sites by kinases other than PKA, which could be pathologic [51]. Another possibility is that even a long-term enhancement in lusitropy, such as associated with greater phosphorylation of MLC2V, might ultimately lead to a chronic disease phenotype through unrecognized negative long-term consequences of this enhanced profile.…”

PP2A as a master regulator of the cell cycle

“…PP2A is one of the most complex members in the PPP family, regulating diverse physiological and cellular processes such as neuronal stabilization, cardiac muscle function and the cell cycle. As such, it is implicated in many human diseases such as Alzheimer’s disease, cardiac disease and cancer (Eichhorn et al ., 2009; Heijman et al ., 2013; Kotlo et al ., 2012; Martin et al ., 2013). PP2A affects such variety of processes due to the formation of diverse heterotrimeric holoenzymes.…”

Transmural gradients of myocardial structure and mechanics: Implications for fiber stress and strain in pressure overload

“…Toepfer, et al (Toepfer et al, 2013) also demonstrated that increased phosphorylation in rat trabeculae enhanced myocardial performance and suggested that decreased MLC-phosphorylation in cardiac disease is a key contributor to impaired cardiac contractile function. MLC phosphorylation levels were significantly reduced in pressure overloaded and failing hearts (Kotlo et al, 2012), but heart failure was prevented in MLC kinase-overexpressing mice (Warren et al, 2012). Additionally, constitutively phosphorylated cardiac MLC in mice was sufficient to prevent a hypertrophic cardiomyopathy phenotype (Karabina et al, 2015), (Yuan et al, 2015).…”