The Akt signaling pathway determines the different proliferative capacity of chronic lymphocytic leukemia B-cells from patients with progressive and stable disease

Chronic lymphocytic leukemia (CLL) B-cells are hyporesponsive to many proliferative signals that induce activation of normal B-lymphocytes. However, a heterogeneous response has recently been observed with immunostimulatory CpG-oligodeoxynucleotides (CpG ODN). We now show that CpG ODN induce proliferation mainly in CLL B-cells from patients with progressive disease and unmutated immunoglobulin V(H) genes, whereas G(1)/S cell cycle arrest and apoptosis are induced in leukemic B-cells from stable/V(H) mutated CLL. Examination of early signaling events demonstrated that all CLL B-cells respond to CpG ODN stimulation by degradation of the NF-kappaB inhibitor IkappaB and activation of the Akt, ERK, JNK and p38 MAPK kinases, but the magnitude and duration of the signaling response was greater in the proliferating cases. Pharmacological inhibition of these pathways showed that simultaneous activation of Akt, ERK and JNK is required for cell cycle progression and proliferation. Conversely, introduction of constitutively active Akt in nonproliferating CLL B-cells resulted in induction of cyclin A following CpG ODN stimulation, indicating that increased Akt activation is sufficient to overcome the hyporesponsiveness of these cells to proliferative signals. Thus, the magnitude of Akt signaling may determine the distinct responses observed in leukemic B-cells belonging to the different prognostic subgroups.

Identification and characterization of a new member of the gas3/PMP22 gene family in C. elegans

The Gas3/PMP22 protein family is characterized by tetraspan transmembrane proteins. The gas3/PMP22 gene is highly expressed in Schwann cells of the peripheral nervous system, and different alterations of this gene are associated with hereditary demyelinating neuropathies, such as the Charcot-Marie-Tooth type 1A, the Dejerine-Sottas syndrome and the Hereditary Liability to Pressure Palsies (HNPP).Here, we report on the identification of at least one member of the Gas3/PMP22 family in the nematode C. elegans (C01C10.1b). C01C10.1b shares 36% of identical amino acids with the human Gas3/PMP22 and is characterized by four hydrophobic putative transmembrane domains. It lacks the typical N-linked glycosylation consensus in the first extracellular loop. C01C10.1b is transcribed as an operon downstream to the gene C01C10.1a, which encodes for a putative tetraspan protein with less conserved homology with the Gas3/PMP22 family. Interestingly, C01C10.1a contains three N-glycosylation sites at the C-terminus. Both genes are expressed in different nematode developmental stages and in the adults. The characterization of one member of the gas3/PMP22 family in C. elegans gives the opportunity to use this model organism to investigate the role of gas3/PMP22 in the regulation of cell proliferation and differentiation and its relation to the hereditary neurodegenerative diseases in humans.