A HMG-COA LYASE ISOFORM CODIFICATED BY HHMGCII1 GENE INTERACTS WITH TUBULIN

PREVITALI G; ARNEDO M; MONESTEROLO N; CAMPETELLI A; PIE-JUSTE J; CASALE C

Mar del Plata, Córdoba

Congreso; Sociedad Argentina de investigación Bioquímica y Biología Molecular; 2007

SAIB

Acetoacetyl-CoA thiolase and 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase are enzymes that participate in the HMG-CoA-generating system in hepatic cholesterogenesis and ketogenesis, they exhibit dual mitochondrial and cytoplasmic localization. In contrast, HMG-CoA lyase (HL), an enzyme proper of ketogenesis, appears to be localized in mitochondrion. The identity and regulation of these enzymes remain unclear. Recently in our laboratory, a HMG-CoA lyase new gene (HMGCLL1) has been cloned. Kinetic analysis showed that the product of HMGCLL1, HL-like, has a similar behavior to HMG-CoA lyase activity found in the cytosolic fraction of mouse testicle. Confocal images of cultured cells transfected with the HMGCLL1 gene shows that HL-like co-localized with cytoskeleton and endoplasmic reticulum proteins, indicating that cytoplasmic ketogenesis could occur. In this work, biochemical and immunofluorescent experiments show that: a) HL-like is a peripheral protein of endoplasmic reticulum, b) In vitro, HL-like interacts with tubulin, c) In vitro, tubulin activates HL-like approximately 50 times and d) the cytosolic lyase activity was affected by taxol and nocodazol in cultured cells. These results suggest that tubulin can be involved in the regulation of the cytosolic HMGCoA lyase activity, which is carried out by the HMGCLL1 gene product.