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SPARC promotes pericyte recruitment via inhibition of endoglin-dependent TGF-β1 activity.

The Journal of cell biology (2011-06-29)
Lee B Rivera, Rolf A Brekken
ABSTRACT

Pericytes migrate to nascent vessels and promote vessel stability. Recently, we reported that secreted protein acidic and rich in cysteine (SPARC)-deficient mice exhibited decreased pericyte-associated vessels in an orthotopic model of pancreatic cancer, suggesting that SPARC influences pericyte behavior. In this paper, we report that SPARC promotes pericyte migration by regulating the function of endoglin, a TGF-β1 accessory receptor. Primary SPARC-deficient pericytes exhibited increased basal TGF-β1 activity and decreased cell migration, an effect blocked by inhibiting TGF-β1. Furthermore, TGF-β-mediated inhibition of pericyte migration was dependent on endoglin and αV integrin. SPARC interacted directly with endoglin and reduced endoglin interaction with αV integrin. SPARC deficiency resulted in endoglin-mediated blockade of pericyte migration, aberrant association of endoglin in focal complexes, an increase in αV integrins present in endoglin immunoprecipitates, and enhanced αV integrin-mediated activation of TGF-β. These results demonstrate that SPARC promotes pericyte migration by diminishing TGF-β activity and identify a novel function for endoglin in controlling pericyte behavior.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Anti-Vinculin antibody produced in rabbit, affinity isolated antibody, buffered aqueous solution
Sigma-Aldrich
Anti-Integrin alphaV Antibody, CT, Intracellular, serum, Chemicon®
Sigma-Aldrich
Anti-NG2 Chondroitin Sulfate Proteoglycan Antibody, Chemicon®, from rabbit
Sigma-Aldrich
Anti-Desmin Antibody, serum, Chemicon®
Sigma-Aldrich
Endoglin human, recombinant, expressed in Sf9 cells, ≥95% (SDS-PAGE), ≥95% (HPLC)