Molecular Basis of ABHD5 Lipolysis Activation

Abstract

Alpha-beta hydrolase domain-containing 5 (ABHD5), the defective gene in human Chanarin-Dorfman syndrome, is a highly conserved regulator of adipose triglyceride lipase (ATGL)-mediated lipolysis that plays important roles in metabolism, tumor progression, viral replication, and skin barrier formation. The structural determinants of ABHD5 lipolysis activation, however, are unknown. We performed comparative evolutionary analysis and structural modeling of ABHD5 and ABHD4, a functionally distinct paralog that diverged from ABHD5 ~500 million years ago, to identify determinants of ABHD5 lipolysis activation. Two highly conserved ABHD5 amino acids (R299 and G328) enabled ABHD4 (ABHD4 N303R/S332G) to activate ATGL in Cos7 cells, brown adipocytes, and artificial lipid droplets. The corresponding ABHD5 mutations (ABHD5 R299N and ABHD5 G328S) selectively disrupted lipolysis without affecting ATGL lipid droplet translocation or ABHD5 interactions with perilipin proteins and ABHD5 ligands, demonstrating that ABHD5 lipase activation could be dissociated from its other functions. Structural modeling placed ABHD5 R299/G328 and R303/G332 from gain-of-function ABHD4 in close proximity on the ABHD protein surface, indicating they form part of a novel functional surface required for lipase activation. These data demonstrate distinct ABHD5 functional properties and provide new insights into the functional evolution of ABHD family members and the structural basis of lipase regulation.

Critical roles for α/β hydrolase domain 5 (ABHD5)/comparative gene identification-58 (CGI-58) at the lipid droplet interface and beyond

“…Several independent groups have likewise found that CGI-58 co-activates ATGL during catecholamine-stimulated lipolysis in adipocytes [20–25]. Recently, the structural determinants of CGI-58-mediated ATGL co-activation in adipocytes have also been clarified [26,27]. Removal of N -terminal amino acids 10–31 of CGI-58 disrupts both CGI-58’s ability to localize to lipid droplets and its ability to co-activate ATGL [26].…”

“…Within the N -terminus, three tryptophan residues (Trp21, Trp25, and Trp29) help form a tether for CGI-58 to stably interact with cytosolic lipid droplets [26]. Using a domain swapping approach from ABHD5 to a structurally similar variant of the α/β hydrolase domain-containing family ABHD4, Sanders and colleagues determined that two conserved amino acids (R299 and G328) were sufficient to confer ATGL co-activation onto ABHD4 [27]. In parallel, mutations of R299 and G328 residues in ABHD5 reduced adipocyte lipolysis without altering CGI-58’s interaction with perilipin [27].…”

“…Using a domain swapping approach from ABHD5 to a structurally similar variant of the α/β hydrolase domain-containing family ABHD4, Sanders and colleagues determined that two conserved amino acids (R299 and G328) were sufficient to confer ATGL co-activation onto ABHD4 [27]. In parallel, mutations of R299 and G328 residues in ABHD5 reduced adipocyte lipolysis without altering CGI-58’s interaction with perilipin [27]. These studies provide important clues into the structural determinants by which CGI-58 regulates lipase activity [26,27].…”

“…In parallel, mutations of R299 and G328 residues in ABHD5 reduced adipocyte lipolysis without altering CGI-58’s interaction with perilipin [27]. These studies provide important clues into the structural determinants by which CGI-58 regulates lipase activity [26,27]. Another recent study also demonstrated that cytosolic fatty acid binding proteins (FABP) directly interact with CGI-58 within its helix-loop-helix cap region, and FABP-CGI-58 interactions facilitate ATGL-mediated lipolysis [28].…”

Mapping Protein Targets of Bioactive Small Molecules Using Lipid-Based Chemical Proteomics

“…The binding and activation of PNPLA2 by ABHD5 is negatively regulated by perilipin (PLIN) proteins (Fig. 2a), 15, 16, 19, 21 and inhibitors of ABHD5-PLIN interactions may thus serve as chemical probes and pharmacotherapies to promote fat lipolysis. 15 Recently, Sanders and colleagues 15 reported the discovery of two structurally distinct ligands for ABHD5—SR-4559, 4 and SR-4995, 5 (Fig.…”