The immunomodulatory protein SV‐IV protects serum‐deprived cells against apoptosis but not against G0/G1 arrest: Possible implications for the survival of implanting embryo

Abstract

Serum deprivation induced in human lymphoblastoid Raji cells oxidative stress-associated apoptotic death and G0/G1 cell cycle arrest. Addition into culture medium of the immunomodulatory protein Seminal vesicle protein 4 (SV-IV) protected these cells against apoptosis but not against cycle arrest. The antiapoptotic activity was related to: (1) decrease of endocellular reactive Oxygen species (ROS) (2) increase of mRNAs encoding anti-oxidant enzymes (catalase, G6PD) and antiapoptotic proteins (survivin, cox-1, Hsp70, c-Fos); (3) decrease of mRNAs encoding proapoptotic proteins (c-myc, Bax, caspase-3, Apaf-1). The biochemical changes underlaying these effects were probably induced by a protein tyrosine kinase (PTK) activity triggered by the binding of SV-IV to its putative plasma membrane receptors. The ineffectiveness of SV-IV to abrogate the cycle arrest was accounted for by its downregulating effects on D1,3/E G1-cyclins and CdK2/4 gene expression, ppRb/pRb ratio, and intracellular ROS concentration. In conclusion, these experiments: (1) prove that SV-IV acts as a cell survival factor; (2) suggest the involvement of a PTK in SV-IV signaling; (3) point to cell cycle-linked enzyme inhibition as responsible for cycle arrest; (4) provide a model to dissect the cycle arrest and apoptosis induced by serum withdrawal; (5) imply a possible role of SV-IV in the survival of hemiallogenic implanting embryos.

Anti-apoptotic seminal vesicle protein IV inhibits cell-mediated immunity

“…2).These data are consistent with similar binding observations already published (Metafora et al, 1989;Morelli et al, 2007). (Stiuso et al, 1999;Romano-Carratelli et al, 2002).…”

“…Similar results were obtained with resting or antigen-stimulated CTLs. In addition, the possibility that the immunosuppression was due to aspecific cytotoxic properties can be ruled out by the following observations: 1) immunosuppression was detectable on activated MNC (see Results) only at low concentrations (5 to 30 M), rich in biologically active SV-IV monomers; at similar low concentrations SV-IV did not inhibit but, in contrast, stimulated quiescent lymphocytes to synthesize and release specific cytokines (Tufano et al, 1996); 2) at concentrations higher than 30 M, rich in biologically inactive SV-IV trimers, no cytotoxic effects were observed (Stiuso et al, 1999); 3) the inhibitory effects of SV-IV on proliferation were found only for immunocompetent cells (Metafora et al, 1989); 4) in addition, SV-IV has been recently demonstrated to possess intrinsic antiapoptotic activity (Morelli et al, 2007).…”

“…These SV-IV-induced immunosuppressive findings are in line with the protective effect of SV-IV on Raji, K562, and Daudi target cells against the NK cytotoxicity (see Results). In this setting it appears also relevant: 1) the SV-IV ability to activate mast cell degranulation with release of immunosuppressive and antiapoptotic histamine and TGF- (Hansson et al, 1999;Metafora et al, manuscript in preparation); 2) the SV-IV ability to protect mouse zygote growth up to blastocyst stage in the semi-solid Fell and Robison culture medium nonpermissive for fertilized egg early development (Morelli et al, 2007). 3) other data showing the critical role of oxidative stress in jeopardizing embryo survival during early development (Guerin et al, 2001).…”

“…Other data indicate that the putative SV-IV receptors probably signal via a protein tyrosine kinaseoperated pathway (Morelli et al, 2007).…”

“…SV-IV possesses a nonspecies-specific ability to modulate inflammation and humoral and cellmediated immune response (Metafora et al, 1989;Peluso et al, 1994;Romano-Carratelli et al, 1995;Tufano et al, 1996;Santagada et al, 2002), to stimulate horseradish and Se-dependent peroxidases (Metafora et al, 2001 and unpublished data), to protect its target cells against oxidative stress-associated apoptosis and, in particular, to defend nonself epididymal spermatozoa from immunological or reactive oxygen species (ROS) attacks in the female genital tract (Paonessa et al, 1984;Morelli et al, 2007). The anti-inflammatory properties are related to phospholipase A 2 (PLA 2 ) inhibition (Metafora et al, 1989), whereas the pro-inflammatory features are based on SV-IV ability to stimulate mast-cell and basophil degranulation with concurrent release of histamine and other mediators (Metafora et al, manuscript in preparation).…”