alpha-actinin-2 couples to cardiac Kv1.5 channels, regulating current density and channel localization in HEK cells.
ABSTRACT Voltage-gated K(+) (Kv) channels are particularly important in the physiology of excitable cells in the heart and the brain. PSD-95 is known to cluster Shaker channels and NMDA receptors and the latter is known to couple through alpha-actinin-2 to the post-synaptic cytoskeleton [Wyszynski et al. (1997) Nature 385, 439-442], but the mechanisms by which Kv channels are linked to the actin cytoskeleton and clustered at specific sites in the heart are unknown. Here we provide evidence that Kv1.5 channels, widely expressed in the cardiovascular system, bind with alpha-actinin-2. Human Kv1.5 interacts via its N-terminus/core region and can be immunoprecipitated with alpha-actinin-2 both after in vitro translation and from HEK cells expressing both proteins. The ion channels and alpha-actinin-2 co-localize at the membrane in HEK cells, where disruption of the actin cytoskeleton and antisense constructs to alpha-actinin-2 modulate the ion and gating current density.
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ABSTRACT: Filamins are important actin cross-linking proteins implicated in scaffolding, membrane stabilization and signal transduction, through interaction with ion channels, receptors and signaling proteins. Here we report the physical and functional interaction between filamins and polycystin-2, a TRP-type cation channel mutated in 10-15% patients with autosomal dominant polycystic kidney disease. Yeast two-hybrid and GST pull-down experiments demonstrated that the C-termini of filamin isoforms A, B and C directly bind to both the intracellular N- and C-termini of polycystin-2. Reciprocal co-immunoprecipitation experiments showed that endogenous polycystin-2 and filamins are in the same complexes in renal epithelial cells and human melanoma A7 cells. We then examined the effect of filamin on polycystin-2 channel function by electrophysiology studies with a lipid bilayer reconstitution system and found that filamin-A substantially inhibits polycystin-2 channel activity. Our study indicates that filamins are important regulators of polycystin-2 channel function, and further links actin cytoskeletal dynamics to the regulation of this channel protein.PLoS ONE 01/2012; 7(7):e40448. · 4.09 Impact Factor
Article: The evolution of skeletal muscle performance: gene duplication and divergence of human sarcomeric alpha-actinins.[show abstract] [hide abstract]
ABSTRACT: In humans, there are two skeletal muscle alpha-actinins, encoded by ACTN2 and ACTN3, and the ACTN3 genotype is associated with human athletic performance. Remarkably, approximately 1 billion people worldwide are deficient in alpha-actinin-3 due to the common ACTN3 R577X polymorphism. The alpha-actinins are an ancient family of actin-binding proteins with structural, signalling and metabolic functions. The skeletal muscle alpha-actinins diverged approximately 250-300 million years ago, and ACTN3 has since developed restricted expression in fast muscle fibres. Despite ACTN2 and ACTN3 retaining considerable sequence similarity, it is likely that following duplication there was a divergence in function explaining why alpha-actinin-2 cannot completely compensate for the absence of alpha-actinin-3. This paper focuses on the role of skeletal muscle alpha-actinins, and how possible changes in functions between these duplicates fit in the context of gene duplication paradigms.BioEssays 12/2009; 32(1):17-25. · 4.95 Impact Factor