Ca²⁺-Dependent Interaction of S100A1 with F₁-ATPase Leads to an Increased ATP Content in Cardiomyocytes

Abstract

S100A1, a Ca2؉ -sensing protein of the EF-hand family that is expressed predominantly in cardiac muscle, plays a pivotal role in cardiac contractility in vitro and in vivo. It has recently been demonstrated that by restoring Ca 2؉ homeostasis, S100A1 was able to rescue contractile dysfunction in failing rat hearts. Myocardial contractility is regulated not only by Ca 2؉ homeostasis but also by energy metabolism, in particular the production of ATP. Here, we report a novel interaction of S100A1 with mitochondrial F 1 -ATPase, which affects F 1 -ATPase activity and cellular ATP production. In particular, cardiomyocytes that overexpress S100A1 exhibited a higher ATP content than control cells, whereas knockdown of S100A1 expression decreased ATP levels. In pull-down experiments, we identified the ␣-and ␤-chain of F 1 -ATPase to interact with S100A1 in a Ca 2؉ -dependent manner. The interaction was confirmed by colocalization studies of S100A1 and F 1 -ATPase and the analysis of the S100A1-F 1 -ATPase complex by gel filtration chromatography. The functional impact of this association is highlighted by an S100A1-mediated increase of F 1 -ATPase activity. Consistently, ATP synthase activity is reduced in cardiomyocytes from S100A1 knockout mice. Our data indicate that S100A1 might play a key role in cardiac energy metabolism. S100 proteins are a family of soluble, EF-hand Ca 2ϩ -binding proteins which exhibit a remarkable cell-and tissue-specific expression pattern. They are involved in numerous intracellular activities, such as cell proliferation and differentiation, or the dynamics of cytoskeletal constituents (reviewed in references 4, 9, and 30). The most abundant S100 protein in the heart is S100A1 (12; reviewed in reference 4). It has been recognized recently as a positive inotropic intracellular regulator of cardiac as well as skeletal muscle Ca 2ϩ homeostasis and contractility (15,16,18,19,20). Accordingly, S100A1-deficient mice exhibited an impaired cardiac contractility response to hemodynamic stress (5). Notably, the absence of S100A1 significantly accelerates the development of contractile dysfunction after myocardial infarction, with a rapid onset of cardiac remodeling and a transition to heart failure combined with excessive mortality (21). Normal contractile function and Ca 2ϩ homeostasis, on the other hand, could be restored in failing myocardium in postinfarcted rat hearts by S100A1 gene delivery (19).In addition to Ca 2ϩ homeostasis, myocardial workload depends on cardiac metabolism. As the energy demand changes, the flux through the mitochondrial ATP synthase (F 1 F oATPase), which is responsible for the bulk of ATP synthesis in the myocardium, must change so that ATP synthesis matches ATP consumption (reviewed in references 6 and 10). To sustain cardiac function in all possible situations, there has to be a strict correlation between energy production, energy transfer, and energy utilization (reviewed in reference 29). In this regard, Ca 2ϩ has emerged as a major factor for adapting mitochondrial A...

Targeting S100A1 in heart failure

“…[47][48][49] When overexpressed in CM, S100A1 augments cytosolic ATP content, whereas siRNA-mediated S100A1 knockdown generated the opposite effect. 47 The adenosine nucleotide translocator, mediating the exchange of ADP and ATP between the mitochondrial matrix and the cytoplasm, was characterized as a second mitochondrial target for S100A1. 47,49 This finding prompts speculation that facilitated mitochondrial ATP efflux might in part contribute to cytosolic ATP elevations.…”

“…Subsequent co-immunoprecipitation and functional studies corroborated its mitochondrial presence through detection and modulation of several mitochondrial target proteins both located in the matrix and the intramembranous space. 47 The mitochondrial ATP synthase is the most important enzyme for ATP production in mammals and plants and S100A1 was found to directly interact with the F1 portion (a/b-chain), stimulating ATP synthase activity and increasing ATP content in CM. [47][48][49] When overexpressed in CM, S100A1 augments cytosolic ATP content, whereas siRNA-mediated S100A1 knockdown generated the opposite effect.…”

“…47 The mitochondrial ATP synthase is the most important enzyme for ATP production in mammals and plants and S100A1 was found to directly interact with the F1 portion (a/b-chain), stimulating ATP synthase activity and increasing ATP content in CM. [47][48][49] When overexpressed in CM, S100A1 augments cytosolic ATP content, whereas siRNA-mediated S100A1 knockdown generated the opposite effect. 47 The adenosine nucleotide translocator, mediating the exchange of ADP and ATP between the mitochondrial matrix and the cytoplasm, was characterized as a second mitochondrial target for S100A1.…”

“…47 The adenosine nucleotide translocator, mediating the exchange of ADP and ATP between the mitochondrial matrix and the cytoplasm, was characterized as a second mitochondrial target for S100A1. 47,49 This finding prompts speculation that facilitated mitochondrial ATP efflux might in part contribute to cytosolic ATP elevations. As S100A1 also protects CM from apoptosis and anti-apoptotic effects have been assigned to the adenosine nucleotide translocator, it is tempting to speculate that the S100A1/adenosine nucleotide translocator interaction might participate in protection from programmed cell death in CM (Boerries and Voelkers, unpublished observations).…”

“…47,49 However, despite these promising findings, the precise regulation of mitochondrial integrity and energy production by S100A1 requires in-depth investigation and is subject of ongoing studies.…”