REEP2

REEP2 is an endoplasmic reticulum (ER)-shaping protein that maintains tubular ER morphology through membrane-embedded hydrophobic segments and modulates vesicular trafficking and receptor signaling. REEP2 physically associates with select GPCRs—including T1R2/T1R3 sweet taste receptors and α2C adrenergic receptors—recruiting them into lipid raft microdomains or enhancing ER cargo capacity to increase their surface delivery (PMID:20943918, PMID:24098485). Upon DNA damage, p53 transcriptionally induces REEP2, extending peripheral tubular ER and increasing ER–mitochondria contact sites to promote calcium transfer and apoptosis (PMID:30030520). Dominant-negative and loss-of-function mutations that impair REEP2 membrane association cause hereditary spastic paraplegia SPG72 (PMID:24388663).

1. 2010 High

   Establishing that REEP2 functions as a GPCR-interacting protein that modulates receptor signaling by recruiting taste receptors into lipid raft microdomains rather than simply increasing surface expression answered how REEP2 influences receptor function at the plasma membrane.

   Evidence Co-immunoprecipitation, lipid raft fractionation, heterologous functional assays, and siRNA knockdown in GLUTag cells

   PMID:20943918

   Open questions at the time

   • Structural basis for selective GPCR interaction not determined
   • Whether lipid raft recruitment mechanism generalizes to non-taste GPCRs unknown
2. 2013 Medium

   Demonstrating that REEP2 localizes to the ER and selectively enhances ER cargo capacity for α2C (but not α2A) adrenergic receptors—with the C-terminal domain required for interaction—revealed a receptor-subtype-specific ER chaperone-like role and linked this function to SPG31 pathology.

   Evidence Immunolocalization, co-immunoprecipitation, glycosidic processing assays, and SPG31 REEP1 mutant expression

   PMID:24098485

   Open questions at the time

   • Molecular determinants of GPCR subtype selectivity remain undefined
   • Whether REEP2 directly alters ER tubule structure to accommodate cargo or acts as a classical chaperone is unresolved
3. 2014 High

   Identifying that REEP2 membrane association is essential for ER morphology and that specific missense mutations (p.Val36Glu, p.Phe72Tyr) disrupt this to cause hereditary spastic paraplegia SPG72 established the first disease mechanism for REEP2 and proved its ER-shaping function is physiologically critical in neurons.

   Evidence In vitro membrane-binding assays with wild-type and mutant constructs, fibroblast ER morphology analysis, genetic segregation in affected families

   PMID:24388663

   Open questions at the time

   • Precise structural mechanism by which hydrophobic hairpins generate membrane curvature not resolved
   • Neuron-specific vulnerability to REEP2 loss not mechanistically explained
4. 2018 High

   Showing that p53 transcriptionally induces REEP2 upon DNA damage to extend tubular ER, increase ER–mitochondria contacts via EI24/VDAC2, and promote Ca²⁺-dependent apoptosis placed REEP2 within the p53-mediated cell death pathway and connected ER remodeling to mitochondrial apoptotic signaling.

   Evidence Live-cell ER imaging, ER-to-mitochondria Ca²⁺ transfer assays, apoptosis assays, p53 transcriptional reporters, and knockdown of REEP1/REEP2/EI24

   PMID:30030520

   Open questions at the time

   • Whether REEP2 directly contacts EI24/VDAC2 or acts indirectly through ER morphology changes is unknown
   • Relative contribution of REEP2 versus REEP1 to the apoptotic response not delineated
5. 2023 Medium

   Discovery that REEP2 negatively regulates adipogenic differentiation of bone marrow mesenchymal stem cells—being downregulated during adipogenesis and restored by HDAC inhibition—extended REEP2 function to a non-neuronal lineage decision context.

   Evidence Gene expression profiling, siRNA and overexpression in BM-MSCs, in vitro adipogenic differentiation assays

   PMID:36879811

   Open questions at the time

   • Downstream signaling pathway by which REEP2 suppresses adipogenesis not identified
   • Whether the anti-adipogenic effect requires ER-shaping activity or a distinct mechanism is unclear
   • Single-lab finding without in vivo confirmation
6. 2025 Medium

   Demonstrating that ZEB1-driven REEP2 upregulation (via miR-183/miR-193a suppression) accelerates ER-exit-site-to-Golgi secretory trafficking of pro-tumorigenic factors to promote metastasis revealed a role for REEP2 in the secretory pathway beyond ER morphology.

   Evidence CRISPRi in vivo screen, miRNA regulation assays, ERES-to-Golgi trafficking assays, syngeneic orthotopic mouse metastasis model, secretome analysis (preprint)

   PMID:41292834

   Open questions at the time

   • Preprint not yet peer-reviewed
   • Mechanism by which REEP2 facilitates ERES-to-Golgi transport (direct COPII interaction vs. ER tubule remodeling) not resolved
   • Whether this secretory function is relevant in non-cancer physiological contexts unknown

• The structural basis for REEP2's membrane curvature activity, its selectivity among GPCR substrates, and the relative contributions of ER shaping versus direct protein–protein interactions to its diverse cellular functions remain unresolved.
• No high-resolution structure of REEP2 in a membrane context
• No reconstitution of REEP2-mediated membrane tubulation with purified components
• Neuron-specific pathomechanism of SPG72 not mechanistically dissected