CKMT1A

CKMT1A is a mitochondrial creatine kinase that participates in the phosphocreatine energy-transfer shuttle linking mitochondrial oxidative phosphorylation to cytosolic ATP replenishment (PMID:28521058). In human brown adipose tissue it is selectively enriched relative to white adipose tissue, where it functions as a modulator of ATP synthase-coupled respiration acting in parallel with UCP1-mediated uncoupled respiration as a distinct energy-expenditure pathway (PMID:27418403). Despite this role in mitochondrial energetics, CKMT1A is not the creatine kinase that governs mitochondrial ATP production through the CKB-AKT-mPTP axis: silencing CKMT1A does not alter sensitivity to F1F0 ATP synthase inhibition, distinguishing it functionally from the cytosolic isoform CKB (PMID:38896801). In hepatocellular carcinoma, CKMT1A acts as the downstream effector of an lncRNA n335586/miR-924 ceRNA circuit, where de-repression of CKMT1A promotes epithelial-mesenchymal transition, migration, and metastasis (PMID:29753758). Beyond these contexts, the enzymatic and structural biology of CKMT1A has not been directly characterized in the available corpus.

1. 2016 Medium

   Established a tissue-specific physiological role by showing CKMT1A is selectively enriched in brown adipose tissue, positioning it within an ATP synthase-coupled energy-expenditure pathway parallel to UCP1.

   Evidence Comparative quantitative proteomics of primary human brown vs. white adipose tissue

   PMID:27418403

   Open questions at the time

   • No direct enzymatic assay or knockdown/knockout in this study
   • Causal contribution to thermogenic energy expenditure not functionally tested
2. 2017 Low

   Linked CKMT1A abundance to oxidative-phosphorylation-coupled energy transfer in muscle, supporting its placement in the phosphocreatine shuttle connecting mitochondrial ATP synthesis to cytosolic demand.

   Evidence Reanalysis of proteomic mass spectrometry dataset from broiler pectoralis muscle (high vs. low feed efficiency)

   PMID:28521058

   Open questions at the time

   • Correlative abundance only, no functional assay of CKMT1A
   • No knockdown or rescue to establish causality
3. 2018 Medium

   Defined a post-transcriptional regulatory circuit and a disease role, identifying CKMT1A as the functional effector of an lncRNA/miRNA ceRNA axis driving cancer cell migration and metastasis.

   Evidence In vitro migration/invasion assays, in vivo metastasis model, and miR-924 binding validation in HCC

   PMID:29753758

   Open questions at the time

   • Mechanism by which CKMT1A promotes EMT not resolved
   • Whether its creatine kinase activity is required for the pro-metastatic effect unknown
4. 2024 Medium

   Resolved which creatine kinase isoform controls mitochondrial ATP production, showing through a negative result that CKMT1A is dispensable for F1F0 ATP synthase inhibitor sensitivity unlike cytosolic CKB.

   Evidence siRNA silencing of CKMT1A/CKMT1B with cell viability and ATP production readouts

   PMID:38896801

   Open questions at the time

   • Does not address CKMT1A's role in other energetic or signaling contexts
   • Single lab, single cell-model dependency
5. 2024 Low

   Added a candidate post-translational modification, identifying CKMT1A as an O-GalNAc glycoprotein substrate of GALNT9 in a glycoproteomic screen.

   Evidence Lectin affinity chromatography and LC-MS/MS in SH-SY5Y cells with GALNT9 knockdown

   PMID:38401583

   Open questions at the time

   • No glycosylation site mapping on CKMT1A
   • Functional consequence of CKMT1A glycosylation not tested specifically

• The direct enzymatic kinetics, structural organization, and the mechanism by which CKMT1A drives EMT remain unresolved.
• No reconstituted creatine kinase activity assay for CKMT1A
• No structural model
• Connection between energy-transfer role and pro-metastatic function unestablished