Selective peptide inhibitors of antiapoptotic cellular and viral Bcl-2 proteins lead to cytochrome c release during latent Kaposi’s sarcoma-associated herpesvirus infection

Abstract

Kaposi’s sarcoma-associated herpesvirus (KSHV) is associated with B-cell lymphomas including primary effusion lymphoma and multicentric Castleman’s disease. KSHV establishes latency within B cells by modulating or mimicking the antiapoptotic Bcl-2 family of proteins to promote cell survival. Our previous BH3 profiling analysis, a functional assay that assesses the contribution of Bcl-2 proteins towards cellular survival, identified two Bcl-2 proteins, cellular Mcl-1 and viral KsBcl-2, as potential regulators of mitochondria polarization within a latently infected B-cell line, Bcbl-1. In this study, we used two novel peptide inhibitors identified in a peptide library screen that selectively bind KsBcl-2 (KL6-7 Y4eK) or KsBcl-2 and Mcl-1 (MS1) in order to decipher the relative contribution of Mcl-1 and KsBcl-2 in maintaining mitochondrial membrane potential. We found treatment with KL6-7 Y4eK and MS1 stimulated a similar amount of cytochrome c release from mitochondria isolated from Bcbl-1 cells, indicating that inhibition of KsBcl-2 alone is sufficient for mitochondrial outer membrane permiabilzation (MOMP) and thus apoptosis during a latent B cell infection. In turn, this study also identified and provides a proof-of-concept for the further development of novel KsBcl-2 inhibitors for the treatment of KSHV-associated B-cell lymphomas via the targeting of latently infected B cells.

Daphnoretin induces reactive oxygen species‑mediated apoptosis in melanoma cells

“…The present results showed that the expression levels of Bax increased, while those of Bcl-2 decreased, suggesting that the Bcl-2 family regulates daphnoretin-induced apoptosis. Previous studies have shown that the Bcl-2 family members release cytochrome c and activated various caspases (37,38). Therefore, the results of the present study indicate that daphnoretin induces the activity of the Bcl-2 family proteins, and promote the release of cytochrome c and Apaf-1, thereby activating caspase-9 and -3, and ultimately inducing apoptosis.…”

Phase I Study of Alvocidib Followed by 7+3 (Cytarabine + Daunorubicin) in Newly Diagnosed Acute Myeloid Leukemia

“…Leukemia dependence on BH3 member proteins was assessed, as previously described (22). For evaluation of MCL-1 dependence, we utilized the MCL-1 binding protein, MS1, with modifications allowing for improved cell penetrance, termed T-MS1 (23). T-MS1 has higher potency and affinity for MCL-1 than NOXA (24).…”

Possible Association of Multicentric Castleman's Disease with Autoimmune Lymphoproliferative Syndrome

“…In addition, HHV-8 infection is reported to increase functional Bcl-2 homolog and mimic the activity of the antiapoptotic (Bcl)-2 family of proteins, which function to inhibit the release of cytochrome c from mitochondria, thereby blocking the initiation of apoptosis in HHV-8-related MCD. 24 , 25 These results suggest that impaired lymphocyte apoptosis is related to MCD and can cause ALPS-like features. Although there are few studies discussing the contribution of apoptosis in the etiology of MCD, lymphocyte apoptosis may play a pivotal role on the pathogenesis of MCD and ALPS.…”