Drosophila TRIM32 cooperates with glycolytic enzymes to promote cell growth

Abstract

Control of tissue and organismal size requires the continual reprogramming of metabolic pathways to integrate biosynthetic and degradative signals. During cell growth and/or proliferation, one such mechanism that promotes the accumulation of cellular material is a switch from oxidative to glycolytic metabolism, whereby glycolytic intermediates are diverted towards anabolic pathways. How this switch is regulated in different tissues is not clear. Herein we identify a novel role for the tripartite motif (TRIM) family member, TRIM32, in the maintenance of glycolytic flux. Using a proteomics approach, we uncovered the glycolytic enzymes Aldolase (Ald) and Phosphoglycerate mutase 78 (Pglym) as TRIM32 interacting proteins. Loss of Drosophila TRIM32, encoded by the thin (tn) gene, showed a reduction in glycolytic activity and amino acid abundance. This altered metabolic profile caused a striking reduction in the overall size of two inherently glycolytic larval tissues – somatic muscles and the developing brain. Consistent with a role for metabolic intermediates in glycolysis‐driven biomass production, nutritional supplementation of amino acids in tn mutants restored muscle mass. Many tumors favor glycolytic metabolism to maximize substrate production for uncontrolled cell growth and proliferation. Remarkably, wing disc‐associated tumor growth is abolished upon loss of TRIM32. Our results reveal a novel connection between TRIM32 and the maintenance of glycolytic enzyme levels and upregulated pathway activity for the sustained growth of normal and cancerous tissue growth. Support or Funding Information This work was supported by a grant through the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) to E.R.G (R01AR060788). J.M.T. is supported by a MIRA award from NIGMS (R35GM119557).

TRIM32: A Multifunctional Protein Involved in Muscle Homeostasis, Glucose Metabolism, and Tumorigenesis

“…Human TRIM32 is expressed in a variety of tissues, including skeletal muscle, with elevated levels eminent in the brain and heart [ 10 ]. The Drosophila ortholog of TRIM32 is enriched in larval and adult muscle tissue and demonstrates structural and functional conservation across species [ 11 , 12 , 13 ]. This review highlights classical and emerging roles of TRIM32 as a multifunctional protein in a multitude of developmental and physiological functions, as well as summarizes its involvement in regulating glycolytic enzymes to promote growth in both normal and cancerous tissues.…”

“…Each NHL repeat is comprised of short stretches of about 40 amino acids. The X-ray structure of the TRIM32 NHL motif reveals a β propeller where each NHL repeat folds into four antiparallel β sheets arranged toroidally around a central axis ( Figure 2 B) [ 12 , 21 ]. These NHL repeats are essential for mediating protein–protein interactions and likely provide substrate specificity [ 2 ].…”

“…LGMD2H pathological mutations cluster in the NHL domain and, intriguingly, the disease-causing amino acids R394H/R1114 and D487N/D1203 are conserved between human and fly TRIM32 protein [ 12 , 21 ]. Comparative thermostability analysis found that the R394H mutation has a lower melting temperature compared with the wild type (WT), indicating that this mutation renders the NHL domain unstable.…”

“…However, abnormal locomotor ability and muscle degeneration were only present upon RNA interference (RNAi) of TRIM32 in muscle, but not in neuronal tissue [ 21 ]. Additional proof that the Drosophila model allows for the autonomous evaluation of TRIM32 muscle function came from experiments whereby expression of a full-length TRIM32 cDNA in muscle tissue rescued the degenerative tn -/- muscles [ 11 , 12 , 13 ]. This Drosophila larval muscle model also lacks adaptive immune cells and muscle stem cells, thus bypassing inflammation and complications associated with muscle tissue damage and repair.…”

“…Elevated levels of lactate hydrogenase (LDH) convert pyruvate to lactate and permit the regeneration of NAD+ levels required to maintain high rates of biomass production [ 103 ]. This upregulation of LDH in larval muscles, combined with the dERR-mediated regulation of carbohydrate metabolism genes, ensures sufficient glycolytic intermediate precursors to support the dramatic growth of larvae post embryogenesis [ 12 , 104 , 105 ]. With increased muscle growth, new sarcomeres are added; however, molecular mechanisms coordinating new sarcomere addition and cell growth are just beginning to be understood [ 106 ].…”