EHD2-mediated restriction of caveolar dynamics regulates cellular lipid uptake

Abstract

26Eps15-homology domain containing protein 2 (EHD2) is a dynamin-related ATPase located at the neck of 27 caveolae, but its physiological function has remained unclear. Here, we found that global genetic ablation 28 of EHD2 in mice led to increased fat accumulation. This organismic phenotype was paralleled at the 29 cellular level by increased lipid uptake via a caveolae-, dynamin-and CD36-dependent pathway, an 30 elevated number of detached caveolae and higher caveolar mobility. Furthermore, EHD2 expression itself 31 was down-regulated in the visceral fat of two obese mouse models and obese patients. Our data suggest 32 that EHD2 controls a cell-autonomous, caveolae-dependent lipid uptake pathway and suggest that low 33 EHD2 expression levels are linked to obesity. 34 35 36 Keywords: EHD2, caveolae, fatty acid uptake, lipid metabolism, obesity 37 38 occurrence of compensatory mechanisms. First, we looked for changes of adiponectin, leptin and insulin 126 plasma levels but did not detect any significant difference in mice lacking EHD2 compared to EHD2 del/+ 127 mice (Fig. S3). Free fatty acid concentration in blood plasma was slightly reduced in EHD2 del/del 128 suggesting a possible increase in fatty acid uptake (Fig. S3). Furthermore, we observed a down-regulation 129 of genes involved in de novo lipogenesis in isolated WAT obtained EHD2 del/del vs. EHD2 del/+ mice or in 130 primary adipocyte cell cultures ( Fig. S5B-D) suggesting that downregulation of lipogenesis is an active 131 mechanism that partially compensates for the increased lipid accumulation. 132 133 134

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.…”

Age attenuates the T‐type CaV3.2‐RyR axis in vascular smooth muscle

“…We next confirmed our results by using a novel EHD2 genetic knockout (KO) mouse model. Since EHD2 localizes to the caveolar neck region of all caveolae, genetic abolition of EHD2 increases ubiquitously detachment of caveolae from the plasma membrane (Matthaeus et al, 2019). In line with these findings, we found detachment of caveolae in EHD2 del/del VSMCs compared to control VSMCs (Figure 4a).…”

“…EHD2 is a dynamin‐related ATPase located at the neck of caveolae, which constitutes a structural component of caveolae involved in controlling the stability and turnover of this organelle (Ludwig et al, 2013; Morén et al, 2012; Stoeber et al, 2016). Knockout or down‐regulation of EHD2 in vivo results in decreased surface association and increased mobility of caveolae, whereas EHD2 overexpression stabilizes caveolae at the plasma membrane (Matthaeus et al, 2019; Morén et al, 2012; Shvets, Bitsikas, Howard, Hansen, & Nichols, 2015; Stoeber et al, 2016). Here we used EHD del/del mice to disturb the stability of caveolae to explore the effect of caveolar microdomains on Ca V 3.2‐RyR axis.…”

“…injected with tamoxifen (30 µg/g body weight/day) for five consecutive days and sacrificed within 2–4 days after the injections. EHD2 del/del or EHD2 del/+ littermates (as control) mice (20–35 weeks each) were used as previously described (Matthaeus et al, 2019). All mice were deeply anesthetized by inhalation of isoflurane until cessation of breathing and then killed by cervical dislocation, and the mesentery arteries were removed.…”

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].…”