SIGNALING MECHANISMS INVOLVED IN THE INTERACTION OF DISINTEGRINS WITH LEUKOCYTES AND TUMOR CELLS

BARJA-FIDALGO, C.(1), COELHO, A.L.J.(1), FREITAS, M.S.(1), OLIVEIRA, A.M.(1), COELHO, R.M.(1), ZINGALI, R.B.(2)

(1)Departamento de Farmacologia, Instituto de Biologia, Universidade do Estado do Rio de Janeiro, (2)Departamento de Bioquímica, CCS, Universidade Federal do Rio de Janeiro.

Integrin-mediated adhesions between cells or cell and extracellular matrix (MEC) transduce to intracellular signals, inducing activation of tyrosine kinase-mediated pathways, mobilization of cytoskeleton, modulating an array of cellular functions and, in some cases, the gene expression. Disintegrins have been reported to inhibit integrin-related functions like adhesion of tumor cell, angiogenesis, platelet aggregation and leukocyte migration. This family of  cystein rich peptides, mono or dimeric, often present an RGD motif in a cystein-holding “hair-pin” looping , are able to be selectively recognized by integrins. We have been studying the effects of monomeric RGD-disintegrins Kistrin (KR-av), Flavoridin (FL-a5>av) and Jarastatin (JT-av>a5, am) and a non-RGD heterodimeric disintegrin, EC3 (-a9, -a4), on human neutrophil (PMN) chemotaxis and apoptosis and also on melanoma cells proliferation. Moreover we have investigated the intracellular signals transduced by the interactions of the DIS with those cells. Our results show that all DIS inhibited PMN migration in vitro, although only JT and  EC3 were directly chemotactic to these cells. PMN interaction with JT, KR and EC3, but not FL, induces actin polymerization, tyrosine kinase and focal adhesion kinase (FAK) activation. While JT and KR have activated  MAP kinase pathway, FL and EC3 inhibited this signaling pathway involved in the modulation of apoptosis in PMN. In parallel interaction of RGD-disintegrins in melanoma murine cells (B16F10) inhibited proliferation in vitro. KR and FL, but not JT, were able to induce reorganization of actin cytoskeleton and MAPK activation pathway in melanoma cells. However, cel interactio with KR and JT, but not FL, stimulated c-Fos transcription factor which is involved in the modulation of proliferation. Taken together our data suggest that the snake venoms disintegrins are putative prototypes for the study and the therapeutic control of inflammation process and tumor cells proliferation. (FAPERJ, CNPq, UERJ-SR2, Brazil)

CORRESPONDENCE TO:

BARJA-FIDALGO, C., Rua Pinto Guedes 44 apto 501, Rio de Janeiro, RJ, CEP: 20511-320, Brasil, Email: barja-fidalgo@uerj.br