title: Removal of the BH4 domain from Bcl-2 protein triggers an autophagic process that impairs tumor growth.
abstract: Here, we show that forced expression of a B-cell lymphoma 2 (bcl-2) protein lacking residues 1 to 36 at the N-terminal, including the entire Bcl-2 homology 4 (BH4) domain, determines reduction of in vitro and in vivo human melanoma growth. Noteworthy, melanoma cells in vivo exhibit markedly increased autophagy, as response to expression of bcl-2 protein deleted of its BH4 domain. This observation led to the identification of a novel gain of function for bcl-2 protein lacking the BH4 domain. In particular, upon different autophagic stimuli in vitro, overexpression of bcl-2 protein deleted of BH4 domain induces autophagosome accumulation, conversion of microtubule-associated protein 1 light chain 3B-II, reduced expression of p62/SQSTM1 protein, and thereby enhanced autophagic flux. The relevance of Beclin-1 is evidenced by the fact that 1) the autophagy-promoting and growth-inhibiting properties are partially rescued by Beclin-1 knockdown in cells expressing bcl-2 protein lacking the BH4 domain, 2) Beclin-1 only interacts with wild-type but not with deleted bcl-2, and 3) BH4 domain removal from bcl-2 protein does not influence in vitro and in vivo growth of tumor cells expressing low levels of endogenous Beclin-1. These results provide new insight into molecular mechanism of bcl-2 functions and represent a rationale for the development of agents interfering with the BH4 domain of bcl-2 protein.
authors.affiliation: Experimental Chemotherapy Laboratory, Regina Elena National Cancer Institute, Rome, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Trisciuoglio
authors.forename: Teresa
authors.initials: T
authors.lastname: De Luca
authors.forename: Marianna
authors.initials: M
authors.lastname: Desideri
authors.forename: Daniela
authors.initials: D
authors.lastname: Passeri
authors.forename: Chiara
authors.initials: C
authors.lastname: Gabellini
authors.forename: Stefania
authors.initials: S
authors.lastname: Scarpino
authors.forename: Chengyu
authors.initials: C
authors.lastname: Liang
authors.forename: Augusto
authors.initials: A
authors.lastname: Orlandi
authors.forename: Donatella
authors.initials: D
authors.lastname: Del Bufalo
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001343:Autophagy / Q000235:genetics; D000071186:Beclin-1; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D055785:Gene Knockdown Techniques; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D014183:Transplantation, Heterologous
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D019253:Proto-Oncogene Proteins c-bcl-2