Research Development Foundation

Peter C Gray

Wylie Walker Vale, Jr

Craig A Harrison

Kathy A Lewis

Louise M Bilezikjian

Amy L Blount

Senyon Choe

Wolfgang Fischer

Jonathan A Kelber

Gidi Shani

Cripto, a developmental oncoprotein, antagonizes activin and TGF-b signaling by forming a complex with activin and TGF-b and their type II receptors. This complex precludes the formation of a functional activin/TGF-b&#x2022;type II&#x2022;type I complex, thereby blocking the signaling of activin and TGF-b. Cripto may be generally capable of blocking antiproliferative Smad2/3 signals and provides a novel mechanism of oncogenic action with multiple therapeutic implications. Inhibiting the formation of Cripto and activin/TGF-b complex may enhance antiproliferative effects of activin and TGF-b.

Cripto antagonism of activin and TGF-b signaling

Members of the TGF-&#x3b2; superfamily control many physiologic and pathophysiologic processes in multiple tissues and signal via type II and type I receptor serine kinases. Type II activin receptors are promiscuous and known to bind 12 TGF-&#x3b2; ligands including activins, myostatin, BMPs and nodal. Methods are described for the screening and identification of antagonist for TGF-&#x3b2; superfamily members, in particular activin-A antagonist.

Activin-A mutants

Inhibins and activins are protein hormones that reciprocally modulate a diversity of regulatory pathways. Competitive binding experiments revealed that betaglycan, the type III TGF-&#x3b2; receptor, also functions as an inhibin receptor. Betaglycan augments the binding of inhibin to the ActRII activin receptor. By augmenting inhibin binding to ActRII, betaglycan effectively sequesters ActRII away from activin and thereby reduces activin signaling. In addition, the ActRII-betaglycan complex may generate novel signals distinct from those initiated by activin signaling via ActRII and ALK4. Betaglycan is produced in discrete nuclei of the rat brain and by specific cell types within the adult rat pituitary, testis, and ovary. The presence of betaglycan within inhibin-responsive tissues and cell types, together with the ability of this protoglycan to bind inhibin and to confer inhibin sensitivity, is consistent with a role of betaglycan as an inhibin-specific receptor mediating inhibin responses within various tissues.

Method of inhibiting the formation of inhibin/betaglycan complexes with an anti-betaglycan antibody

Inhibins and activins are protein hormones that reciprocally modulate a diversity of regulatory pathways. Competitive binding experiments revealed that betaglycan, the type III TGF-&bgr; receptor, also functions as an inhibin receptor. Betaglycan augments the binding of inhibin to the ActRII activin receptor. By augmenting inhibin binding to ActRII, betaglycan effectively sequesters ActRII away from activin and thereby reduces activin signaling. In addition, the ActRII-betaglycan complex may generate novel signals distinct from those initiated by activin signaling via ActRII and ALK4. Betaglycan is produced in discrete nuclei of the rat brain and by specific cell types within the adult rat pituitary, testis, and ovary. The presence of betaglycan within inhibin-responsive tissues and cell types, together with the ability of this protoglycan to bind inhibin and to confer inhibin sensitivity, is consistent with a role of betaglycan as an inhibin-specific receptor mediating inhibin responses within various tissues.

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Peter C Gray