The polybasic insertion in autotaxin ? confers specific binding to heparin and cell surface heparan sulfate proteoglycans.

ABSTRACT: Autotaxin (ATX) is a secreted lysophospholipase D that generates the lipid mediator lysophosphatidic acid (LPA), playing a key role in diverse physiological and pathological processes. ATX exists in distinct splice variants, but isoform-specific functions remain elusive. Here we characterize the ATX? isoform, which differs from the canonical form (ATX?) in having a 52-residue polybasic insertion of unknown function in the catalytic domain. We find that the ATX? insertion is susceptible to cleavage by extracellular furin-like endoproteases, but cleaved ATX? remains structurally and functionally intact due to strong interactions within the catalytic domain. Through ELISA and surface plasmon resonance assays, we show that ATX? binds specifically to heparin with high affinity (K(d) ~10(-8) M), whereas ATX? does not; furthermore, heparin moderately enhanced the lysophospholipase D activity of ATX?. We further show that ATX?, but not ATX?, binds abundantly to SKOV3 carcinoma cells. ATX? binding was abolished after treating the cells with heparinase III, but not after chondroitinase treatment. Thus, the ATX? insertion constitutes a cleavable heparin-binding domain that mediates interaction with heparan sulfate proteoglycans, thereby targeting LPA production to the plasma membrane.

SUBMITTER: Houben AJ 

PROVIDER: S-EPMC3537048 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature