EHD2 regulates adipocyte function and is enriched at cell surface–associated lipid droplets in primary human adipocytes

Abstract

Adipocytes play a central role in energy balance, and dysfunctional adipose tissue severely affects systemic energy homeostasis. The ATPase EH domain–containing 2 (EHD2) has previously been shown to regulate caveolae, plasma membrane-specific domains that are involved in lipid uptake and signal transduction. Here, we investigated the role of EHD2 in adipocyte function. We demonstrate that EHD2 protein expression is highly up-regulated at the onset of triglyceride accumulation during adipocyte differentiation. Small interfering RNA–mediated EHD2 silencing affected the differentiation process and impaired insulin sensitivity, lipid storage capacity, and lipolysis. Fluorescence imaging revealed localization of EHD2 to caveolae, close to cell surface–associated lipid droplets in primary human adipocytes. These lipid droplets stained positive for glycerol transporter aquaporin 7 and phosphorylated perilipin-1 following adrenergic stimulation. Further, EHD2 overexpression in human adipocytes increased the lipolytic signaling and suppressed the activity of transcription factor PPARγ. Overall, these data suggest that EHD2 plays a key role for adipocyte function.

Lipid accumulation promotes scission of caveolae

“…Our data shows that a relatively small increase in glycosphingolipids and Chol results in their accumulation in caveolae, reducing the caveolae neck diameter, and driving caveolae scission from the PM. EHD2 was identified to counterbalance the stability of caveolae in response to lipid composition and in accordance with a recent study (Matthäus et al, 2019; Morén et al, 2019), we describe a key regulatory role of EHD2 in lipid homeostasis.…”

“…To be able to quantitatively assess differences in morphology, we differentiated 3T3-L1 cells to adipocytes, which results in upregulation of Cav1 and EHD2 (Fig. S5B) (Morén et al, 2019), and formation of a large number of caveolae (Thorn et al, 2003) that could be clearly distinguished from clathrin-coated pits (Fig. S5C).…”

Keeping in touch with the membrane; protein- and lipid-mediated confinement of caveolae to the cell surface

“…EHD2 is specifically localized to most of the caveolae in cells under normal conditions [8]. Furthermore, the tissue and differentiation specific expression of EHD2 correlates with the expression of the caveolae coat components, suggesting that EHD2 is a fundamental component required for caveolae function [8,40,41]. Interestingly, in contrast with CAV1 and cavin1, EHD2 is located at the neck of caveolae [8,20] and not detected on internal caveolae vesicles, implying that it has a specific role, which is restricted to surface connected caveolae [8,9].…”

Cellular functions and intrinsic attributes of the ATP‐binding Eps15 homology domain‐containing proteins

“…Thus, in this context, EHDs appears to function as a scaffold that restricts the adventitious fission and release of caveolae thereby ensuring that the plasma membrane retains sufficient membrane reservoir to buffer stretch‐induced membrane rupture. Recent results indicate that the loss of EHD2 results in an increased production of lipid droplets, resulting possibly from aberrant caveolae signaling 70,71 as well as from defects in autophagic degradation of lipid droplets via a Rab10 and EHBP1‐dependent pathway 72 …”