Bcl-2 phosphorylation by p38 MAPK - Identification of target sites and biologic consequences
ABSTRACT The antiapoptotic role of Bcl-2 can be regulated by its phosphorylation in serine and threonine residues located in a nonstructured loop that links BH3 and BH4 domains. p38 MAPK has been identified as one of the kinases able to mediate such phosphorylation, through direct interaction with Bcl-2 protein in the mitochondrial compartment. In this study, we identify, by using mass spectrometry techniques and specific anti-phosphopeptide antibodies, Ser(87) and Thr(56) as the Bcl-2 residues phosphorylated by p38 MAPK and show that phosphorylation of these residues is always associated with a decrease in the antiapoptotic potential of Bcl-2 protein. Furthermore, we obtained evidence that p38 MAPK-induced Bcl-2 phosphorylation plays a key role in the early events following serum deprivation in embryonic fibroblasts. Both cytochrome c release and caspase activation triggered by p38 MAPK activation and Bcl-2 phosphorylation are absent in embryonic fibroblasts from p38alpha knock-out mice (p38alpha(-/-) MEF), whereas they occur within 12 h of serum withdrawal in p38alpha(+/+) MEF; moreover, they can be prevented by p38 MAPK inhibitors and are not associated with the synthesis of the proapoptotic proteins Bax and Fas. Thus, Bcl-2 phosphorylation by activated p38 MAPK is a key event in the early induction of apoptosis under conditions of cellular stress.
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ABSTRACT: The microbial source, which includes live, attenuated, or genetically modified microbes or their cellular component(s) or metabolites, has gained increasing significance for therapeutic intervention against several pathophysiological conditions of disease including leukemia, which remains an incurable disease till now despite recent advances in the medical sciences. We therefore took up the present study to explore if the leishmanial lipid (pLLD) isolated from L. donovani can play an anti-neoplastic role in acute myeloid leukemia cells by regulating cellular growth. Indeed pLLD significantly inhibited cell proliferation of four AML cell lines (HL-60, MOLT-4, U937, and K562). Scanning electron microscopy and DNA fragmentation analysis revealed that it significantly induced apoptosis of U937 cells through morphological alteration. Occurrence of apoptosis was checked by using Annexin exposure and this established that the cell cycle was arrested at G0/G1 phase in time-dependent manner. pLLD increased the intracellular ROS with alteration of mitochondrial membrane potential, as detected using DCFDA. It also regulated the expression of apoptosis-related proteins like Bax, Bcl2, Bad and t-Bid besides causing cleavage of PARP as determined by western blot analysis. Treatment of U937 cells with pLLD induced the activation of extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK)1/2, p38, and caspases 9/3. The results suggest that pLLD induces apoptosis in acute myeloid leukemia cells possibly via increasing intracellular ROS and regulating the MAPK pathway.PLoS ONE 03/2015; 10(3):e0120509. DOI:10.1371/journal.pone.0120509 · 3.53 Impact Factor
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ABSTRACT: The G2019S leucine-rich repeat kinase 2 (LRRK2) mutation is the most common cause of genetic Parkinson's disease (PD). However, the molecular mechanism underlying LRRK2 G2019S-induced cellular pathology is poorly understood. Here, we demonstrated that LRRK2 G2019S bound to and phosphorylated Bcl-2, a mitochondrial anti-apoptotic protein, at Threonine 56. Either stable expression of Bcl-2 or transient expression of a Bcl-2 phosphor mutant (Bcl-2T56A) abolished LRRK2 G2019S-induced mitochondrial depolarization and autophagy. Together, our findings reveal a previously unidentified target of LRRK2 G2019S, showing that Bcl-2 serves as a point of crosstalk between LRRK2 G2019S-mediated mitochondrial disorder and dysregulation of autophagy.Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease 11/2014; 1852(1). DOI:10.1016/j.bbadis.2014.11.009 · 5.09 Impact Factor