EH domain proteins regulate cardiac membrane protein targeting.
BACKGROUND
Cardiac membrane excitability is tightly regulated by an integrated network of membrane-associated ion channels, transporters, receptors, and signaling molecules. Membrane protein dynamics in health and disease are maintained by a complex ensemble of intracellular targeting, scaffolding, recycling, and degradation pathways. Surprisingly, despite decades of research linking dysfunction in membrane protein trafficking with human cardiovascular disease, essentially nothing is known regarding the molecular identity or function of these intracellular targeting pathways in excitable cardiomyocytes.


OBJECTIVE
We sought to discover novel pathways for membrane protein targeting in primary cardiomyocytes.


RESULTS
We report the initial characterization of a large family of membrane trafficking proteins in human heart. We used a tissue-wide screen for novel ankyrin-associated trafficking proteins and identified 4 members of a unique Eps15 homology (EH) domain-containing protein family (EHD1, EHD2, EHD3, EHD4) that serve critical roles in endosome-based membrane protein targeting in other cell types. We show that EHD1-4 directly associate with ankyrin, provide the first information on the expression and localization of these molecules in primary cardiomyocytes, and demonstrate that EHD1-4 are coexpressed with ankyrin-B in the myocyte perinuclear region. Notably, the expression of multiple EHD proteins is increased in animal models lacking ankyrin-B, and EHD3-deficient cardiomyocytes display aberrant ankyrin-B localization and selective loss of Na/Ca exchanger expression and function. Finally, we report significant modulation of EHD expression following myocardial infarction, suggesting that these proteins may play a key role in regulating membrane excitability in normal and diseased heart.


CONCLUSIONS
Our findings identify and characterize a new class of cardiac trafficking proteins, define the first group of proteins associated with the ankyrin-based targeting network, and identify potential new targets to modulate membrane excitability in disease. Notably, these data provide the first link between EHD proteins and a human disease model.
Gudmundsson
Hjalti
H
Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, USA.
Hund
Thomas J
TJ
Wright
Patrick J
PJ
Kline
Crystal F
CF
Snyder
Jedidiah S
JS
Qian
Lan
L
Koval
Olha M
OM
Cunha
Shane R
SR
George
Manju
M
Rainey
Mark A
MA
Kashef
Farshid E
FE
Dun
Wen
W
Boyden
Penelope A
PA
Anderson
Mark E
ME
Band
Hamid
H
Mohler
Peter J
PJ
D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D005810:Multigene Family / Q000502:physiology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D033921:Vesicular Transport Proteins / Q000378:metabolism / Q000502:physiology*
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C120700:EHD1 protein, human; C406446:EHD2 protein, human; C406447:EHD3 protein, human; C406448:EHD4 protein, human; D008565:Membrane Proteins; D009687:Nuclear Proteins; D033921:Vesicular Transport Proteins