The tumour suppressor Ras-association domain family protein 1A (RASSF1A) regulates TNF-α signalling in cardiomyocytes.
OBJECTIVE
Tumour necrosis factor-α (TNF-α) plays a key role in the regulation of cardiac contractility. Although cardiomyocytes are known to express the TNF-α receptors (TNFRs), the mechanism of TNF-α signal transmission is incompletely understood. The aim of this study was to investigate whether the tumour suppressor Ras-association domain family protein 1 isoform A (RASSF1A) modulates TNF-α signalling in cardiomyocytes.


RESULTS
We used RASSF1A knockout (RASSF1A(-/-)) mice and wild-type (WT) littermates in this study. Acute stimulation with a low dose of TNF-α (10 µg/kg iv) increased cardiac contractility and intracellular calcium transients' amplitude in WT mice. In contrast, RASSF1A(-/-) mice showed a blunted contractile response. Mechanistically, RASSF1A was essential in the formation of the TNFR complex (TNFRC), where it functions as an adaptor molecule to facilitate the recruitment of TNFR type 1-associated death domain protein and TNFR-associated factor 2 to form the TNF-α receptor complex. In the absence of RASSF1A, signal transmission from the TNF-α receptor complex to the downstream effectors, such as cytoplasmic phospholipase A2 and protein kinase A, was attenuated leading to the reduction in the activation of calcium handling molecules, such as L-type Ca(2+) channel and ryanodine receptors.


CONCLUSIONS
Our data indicate an essential role of RASSF1A in regulating TNF-α signalling in cardiomyocytes, with RASSF1A being key in the formation of the TNFRC and in signal transmission to the downstream targets.
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK Faculty of Pharmacy, Zagazig University, EL-Sharkiah, Egypt J David Gladstone Research Institutes, San Francisco, CA, USA.
Tamer M A
TM
Mohamed
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Min
M
Zi
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Sukhpal
S
Prehar
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Arfa
A
Maqsood
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Riham
R
Abou-Leisa
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Loan
L
Nguyen
Division of Biology, Beckman Research Institute of the City of Hope, Duarte, CA, USA.
Gerd P
GP
Pfeifer
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Elizabeth J
EJ
Cartwright
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
Ludwig
L
Neyses
Institute of Cardiovascular Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK delvac.oceandy@manchester.ac.uk.
Delvac
D
Oceandy
D000818:Animals; D020013:Calcium Signaling; D051379:Mice; D018345:Mice, Knockout; D009200:Myocardial Contraction / Q000502:physiology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction; D053199:TNF Receptor-Associated Death Domain Protein / Q000378:metabolism; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D016328:NF-kappa B; D010446:Peptide Fragments; C496882:RASSF1 protein, mouse; D018124:Receptors, Tumor Necrosis Factor; D053199:TNF Receptor-Associated Death Domain Protein; D047992:TNF Receptor-Associated Factor 2; C481226:Tradd protein, mouse; D014409:Tumor Necrosis Factor-alpha; D025521:Tumor Suppressor Proteins
Calcium transient; Contractile function; RASSF1A; Signal transduction; Tumour necrosis factor alpha