Frontiers in Immunology (Jul 2012)

The salivary scavenger and agglutinin (SALSA) binds MBL and regulates the lectin pathway of complement in solution and on surfaces

  • Martin eParnov Reichhardt,
  • Vuokko eLoimaranta,
  • Steffen eThiel,
  • Jukka eFinne,
  • Seppo eMeri,
  • Seppo eMeri,
  • Hanna eJarva,
  • Hanna eJarva

DOI
https://doi.org/10.3389/fimmu.2012.00205
Journal volume & issue
Vol. 3

Abstract

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The scavenger receptor cysteine-rich (SRCR) protein SALSA, also known as gp340, salivary agglutinin (SAG) and deleted in malignant brain tumor 1 (DMBT1), is a 340 kDa glycoprotein expressed on mucosal surfaces and secreted into several body fluids. SALSA binds to a broad variety of microbes and endogenous ligands, such as complement factor C1q, surfactant proteins D and A (SP-D and SP-A) and IgA. Our search for novel ligands of SALSA by direct protein-interaction studies led to the identification of mannan binding lectin (MBL) as a new binding partner. We observed that surface-associated SALSA activates complement via binding of MBL. On the other hand, soluble SALSA was found to inhibit C. albicans-induced complement activation. Thus, SALSA has a dual complement regulatory function. It activates the lectin pathway when bound to a surface and inhibits it when free in the fluid-phase. These activities are mediated via a direct interaction with MBL.

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