Secreted mutant calreticulins as rogue cytokines in myeloproliferative neoplasms.

Mutant calreticulin (CALR) proteins resulting from a -1/+2 frameshifting mutation of the CALR exon 9 carry a novel C-terminal amino acid sequence and drive the development of myeloproliferative neoplasms (MPNs). Mutant CALRs were shown to interact with and activate the thrombopoietin receptor (TpoR/MPL) in the same cell. We report that mutant CALR proteins are secreted and can be found in patient plasma at levels up to 160 ng/mL, with a mean of 25.64 ng/mL. Plasma mutant CALR is found in complex with soluble transferrin receptor 1 (sTFR1) that acts as a carrier protein and increases mutant CALR half-life. Recombinant mutant CALR proteins bound and activated the TpoR in cell lines and primary megakaryocytic progenitors from patients with mutated CALR in which they drive thrombopoietin-independent colony formation. Importantly, the CALR-sTFR1 complex remains functional for TpoR activation. By bioluminescence resonance energy transfer assay, we show that mutant CALR proteins produced in 1 cell can specifically interact in trans with the TpoR on a target cell. In comparison with cells that only carry TpoR, cells that carry both TpoR and mutant CALR are hypersensitive to exogenous mutant CALR proteins and respond to levels of mutant CALR proteins similar to those in patient plasma. This is consistent with CALR-mutated cells that expose TpoR carrying immature N-linked sugars at the cell surface. Thus, secreted mutant CALR proteins will act more specifically on the MPN clone. In conclusion, a chaperone, CALR, can turn into a rogue cytokine through somatic mutation of its encoding gene.

Hematoxylin binds to mutant calreticulin and disrupts its abnormal interaction with thrombopoietin receptor.

Somatic mutations of calreticulin (CALR) have been identified as a main disease driver of myeloproliferative neoplasms, suggesting that development of drugs targeting mutant CALR is of great significance. Site-directed mutagenesis in the N-glycan binding domain (GBD) abolishes the ability of mutant CALR to oncogenically activate the thrombopoietin receptor (MPL). We therefore hypothesized that a small molecule targeting the GBD might inhibit the oncogenicity of the mutant CALR. Using an in silico molecular docking study, we identified candidate binders to the GBD of CALR. Further experimental validation of the hits identified a group of catechols inducing a selective growth inhibitory effect on cells that depend on oncogenic CALR for survival and proliferation. Apoptosis-inducing effects by the compound were significantly higher in the CALR-mutated cells than in CALR wild-type cells. Additionally, knockout or C-terminal truncation of CALR eliminated drug hypersensitivity in CALR-mutated cells. We experimentally confirmed the direct binding of the selected compound to CALR, disruption of the mutant CALR-MPL interaction, inhibition of the JAK2-STAT5 pathway, and reduction at the intracellular level of mutant CALR upon drug treatment. Our data indicate that small molecules targeting the GBD of CALR can selectively kill CALR-mutated cells by disrupting the CALR-MPL interaction and inhibiting oncogenic signaling.

Calreticulin mutants as oncogenic rogue chaperones for TpoR and traffic-defective pathogenic TpoR mutants.

Calreticulin (CALR) +1 frameshift mutations in exon 9 are prevalent in myeloproliferative neoplasms. Mutant CALRs possess a new C-terminal sequence rich in positively charged amino acids, leading to activation of the thrombopoietin receptor (TpoR/MPL). We show that the new sequence endows the mutant CALR with rogue chaperone activity, stabilizing a dimeric state and transporting TpoR and mutants thereof to the cell surface in states that would not pass quality control; this function is absolutely required for oncogenic transformation. Mutant CALRs determine traffic via the secretory pathway of partially immature TpoR, as they protect N117-linked glycans from further processing in the Golgi apparatus. A number of engineered or disease-associated TpoRs such as TpoR/MPL R102P, which causes congenital thrombocytopenia, are rescued for traffic and function by mutant CALRs, which can also overcome endoplasmic reticulum retention signals on TpoR. In addition to requiring N-glycosylation of TpoR, mutant CALRs require a hydrophobic patch located in the extracellular domain of TpoR to induce TpoR thermal stability and initial intracellular activation, whereas full activation requires cell surface localization of TpoR. Thus, mutant CALRs are rogue chaperones for TpoR and traffic-defective TpoR mutants, a function required for the oncogenic effects.

Functional Specialization of Human Salivary Glands and Origins of Proteins Intrinsic to Human Saliva.

Salivary proteins are essential for maintaining health in the oral cavity and proximal digestive tract, and they serve as potential diagnostic markers for monitoring human health and disease. However, their precise organ origins remain unclear. Through transcriptomic analysis of major adult and fetal salivary glands and integration with the saliva proteome, the blood plasma proteome, and transcriptomes of 28+ organs, we link human saliva proteins to their source, identify salivary-gland-specific genes, and uncover fetal- and adult-specific gene repertoires. Our results also provide insights into the degree of gene retention during gland maturation and suggest that functional diversity among adult gland types is driven by specific dosage combinations of hundreds of transcriptional regulators rather than by a few gland-specific factors. Finally, we demonstrate the heterogeneity of the human acinar cell lineage. Our results pave the way for future investigations into glandular biology and pathology, as well as saliva's use as a diagnostic fluid.

Nonlinear consequences of promotive and prohibitive voice for managers' responses: The roles of voice frequency and LMX.

Departing from past research on managers' responses to employee voice, we propose and examine a nonlinear linkage between promotive/prohibitive voice and managers' evaluations of voicers (i.e., manager-rated voicers' promotability and overall performance). Drawing from social persuasion theory, we theorize that managers tend to give more positive evaluations to employees who engage in a moderate frequency of promotive/prohibitive voice than those who either rarely speak up or speak up very frequently. In Study 1, based on a sample from a Chinese bank, we found that leader-member exchange quality (LMX) moderated the inverted U-shaped linkage of prohibitive voice with manager-rated promotability of voicers, whereas the frequency of promotive voice was not related to promotability, irrespective of levels of LMX. In Study 2, using employee-reported voice frequency, rather than the manager-rated measures adopted in Study 1, we largely replicated the main findings of Study 1 based on a sample from an information technology firm in the United States. In Study 3, using another U.S. sample, from a financial services firm, we found that manager-perceived voice constructiveness mediated the curvilinear interactive effect of prohibitive voice (rather than promotive voice) and LMX on managers' evaluations of employees' overall performance. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Reaching the limits of reciprocity in favor exchange: The effects of generous, stingy, and matched favor giving on social status.

Group members gain social status via giving favors to others, but why and when they do so remain unclear in the literature. Building on social exchange theory and social status literature, we identify three types of favor giving among group members (generous, stingy, and matched) and propose that an affective mechanism (i.e., gratitude) and a cognitive mechanism (i.e., perceived competence) underlie the relationship between favor giving and status attainment. Specifically, generous/stingy favor giving has a linear relationship with status attainment through both gratitude and perceived competence, whereas matched favor giving has a curvilinear relationship with status attainment only through perceived competence. An experimental study and a field study lend support to our propositions. Our study complements the literature by offering a complete picture of how three types of favor giving among group members shape their social status in different ways. (PsycINFO Database Record