SMIM30

SMIM30 is a small integral membrane microprotein encoded by a smORF within the lncRNA LINC00998 whose translated peptide, rather than the RNA, drives its biological activity across cell growth, signaling, and antiviral defense (PMID:32461121, PMID:36495128). In hepatocellular carcinoma, SMIM30 promotes tumorigenesis by anchoring the non-receptor tyrosine kinases SRC and YES1 to the membrane, driving their phosphorylation and activation of downstream MAPK signaling, and its expression is transcriptionally driven by c-Myc (PMID:32461121). Localizing to ER and mitochondrial membranes, the peptide also accelerates the G1/S cell cycle transition by enhancing SERCA pump activity to lower cytosolic calcium, thereby upregulating CDK4, cyclin E2, phosphorylated Rb, and E2F1 (PMID:36495128). Under the alias MAVI1, the same ER-localized microprotein binds mitochondrial MAVS, inhibits MAVS aggregation, and suppresses type I interferon signaling during viral infection, such that its loss in knockout mice attenuates infection and improves survival (PMID:37656786). SMIM30 additionally functions in adipose tissue macrophages, where it modulates inflammatory responses and macrophage-adipocyte communication to maintain insulin sensitivity and systemic metabolic homeostasis (PMID:40549483).

1. 2020 High

   Established that the LINC00998 locus encodes a functional peptide rather than acting as a non-coding RNA, and that this peptide drives HCC by tethering SRC/YES1 to the membrane to activate MAPK signaling.

   Evidence Coding-potential vectors, KD/OE functional assays, and mechanistic studies of kinase membrane anchoring and MAPK activation in HCC cells

   PMID:32461121

   Open questions at the time

   • Direct structural basis for SRC/YES1 membrane anchoring not defined
   • Whether SMIM30 binds SRC/YES1 directly or via an intermediate not resolved
   • In vivo tumor relevance limited to the assays in this study
2. 2022 High

   Linked SMIM30 to ER/mitochondrial membrane localization and cell cycle control, showing it drives G1/S progression through SERCA-dependent calcium lowering rather than RNA function.

   Evidence Subcellular fractionation, stop-codon insertion mutagenesis, calcium chelator and SERCA agonist rescue, flow cytometry, and Western blot for CDK4/cyclin E2/p-Rb/E2F1

   PMID:36495128

   Open questions at the time

   • Direct physical interaction between SMIM30 and SERCA not established
   • Relationship between the SERCA/calcium axis and the SRC/MAPK mechanism unclear
   • Single-lab finding
3. 2023 High

   Identified SMIM30 (MAVI1) as a negative regulator of antiviral innate immunity that binds MAVS and blocks its aggregation, revealing a role distinct from its proliferative functions.

   Evidence Co-IP with MAVS, MAVS aggregation assay, interferon reporter assays, Mavi1-knockout mice in viral infection, and a peptide inhibitor of the MAVI1-MAVS interaction

   PMID:37656786

   Open questions at the time

   • How an ER-localized peptide engages mitochondrial MAVS structurally not defined
   • Connection between antiviral and oncogenic/cell-cycle roles not integrated
   • Therapeutic window of the peptide inhibitor not characterized
4. 2025 Medium

   Extended SMIM30 function to metabolic homeostasis, showing it acts in adipose tissue macrophages to modulate inflammation and preserve insulin sensitivity.

   Evidence Macrophage-specific expression studies, in vivo metabolic phenotyping, and macrophage-adipocyte communication assays

   PMID:40549483

   Open questions at the time

   • Limited mechanistic detail on how SMIM30 modulates inflammatory signaling in macrophages
   • Whether the MAVS/interferon axis underlies the metabolic phenotype not tested
   • Single study

• How SMIM30's distinct membrane-localized activities — MAPK kinase anchoring, SERCA-dependent calcium control, MAVS regulation, and macrophage inflammatory modulation — are mechanistically unified or selectively deployed across tissues remains unresolved.
• No single structural or binding model accounts for the multiple partners
• Tissue- and context-specific partner selection not defined
• Direct binding interfaces with SRC/YES1 and SERCA not mapped