Caride, Ariel J.

Chromosomal translocations leading to expression of abnormal fusion proteins play a major role in the pathogenesis of various hematologic malignancies. The recent development of high‐throughput, “deep” sequencing has allowed discovery of novel translocations leading to a rapid increase in understanding these diseases. Translocations involving the anaplastic lymphoma kinase (ALK) gene leading to ALK fusion proteins originally were discovered in anaplastic large cell lymphomas (ALCLs). Among ALCLs, NPM1‐ALK fusions are most common and lead to nuclear localization of the fusion protein. Here, we present a 50‐year‐old male with ALCL demonstrating cytoplasmic ALK immunoreactivity only, suggesting the presence of a non‐NPM1 fusion partner. We performed deep RNA sequencing of tumor tissue from this patient and identified a novel transcript fusing Exon 6 of TRAF1 to Exon 20 of ALK. The TRAF1‐ALK fusion transcript was confirmed at the mRNA level by Sanger sequencing and the fusion protein was visualized by Western blot. The discovery of this TRAF1‐ALK fusion expands the diversity of known ALK fusion partners and highlights the power of deep sequencing for fusion transcript discovery. © 2013 Wiley Periodicals, Inc.

Plasma-membrane calcium pumps [PMCAs (plasma-membrane Ca2+-ATPases)] expel Ca2+ from eukaryotic cells to maintain overall Ca2+ homoeostasis and to provide local control of intracellular Ca2+ signalling. Recent work indicates functional versatility among PMCA isoforms, with specific pumps being essential for cochlear hair cell function, sperm motility, feedback signalling in the heart and pre- and post-synaptic Ca2+ regulation in neurons. The functional versatility of PMCAs is due to differences in their regulation by CaM (calmodulin), kinases and other signalling proteins, as well as to their differential targeting and retention in defined plasma membrane domains. The basis for this is the structural diversity of PMCAs. In mammals, four genes encode PMCA isoforms 1–4, and each of these has multiple variants generated by alternative RNA splicing. The alternatively spliced regions are intimately involved in the regulatory interactions and differential membrane localization of the pumps. The alternatively spliced C-terminal tail acts as an autoinhibitory domain by interacting with the catalytic core of the pump. The degree of inhibition and the kinetics of interaction with the major activator CaM differ between PMCA variants. This translates into functional differences in how PMCAs handle Ca2+ signals of different magnitude and frequency. Accumulating evidence thus demonstrates how structural diversity provides functional versatility in the PMCAs.