Physiological functions of the TRPM4 channels via protein interactions

Transient Receptor Potential, Melastatin-related, member 4 (TRPM4) channels are Ca²⁺-activated Ca²⁺-impermeable cation channels. These channels are expressed in various types of mammalian tissues including the brain and are implicated in many diverse physiological and pathophysiological conditions. In the past several years, the trafficking processes and regulatory mechanism of these channels and their interacting proteins have been uncovered. Here in this minireview, we summarize the current understanding of the trafficking mechanism of TRPM4 channels on the plasma membrane as well as heteromeric complex formation via protein interactions. We also describe physiological implications of protein-TRPM4 interactions and suggest TRPM4 channels as therapeutic targets in many related diseases. [BMB Reports 2015; 48(1): 1-5]     

Pulmonary Toxocariasis Mimicking Invasive Aspergillosis in a Patient with Ulcerative Colitis

A 45-year-old-male who had underlying ulcerative colitis and presented with fever and dry cough. Initially, the patient was considered to have invasive aspergillosis due to a positive galactomannan assay. He was treated with amphotericin B followed by voriconazole. Nevertheless, the patient deteriorated clinically and radiographically. The lung biopsy revealed eosinophilic pneumonia, and ELISA for Toxocara antigen was positive, leading to a diagnosis of pulmonary toxocariasis. After a 10-day treatment course with albendazole and adjunctive steroids, the patient recovered completely without any sequelae. Pulmonary toxocariasis may be considered in patients with subacute or chronic pneumonia unresponsive to antibiotic agents, particularly in cases with eosinophilia.     

Intracellular regulation of cell signaling cascades: how location makes a difference

Organelles such as endosomes and the Golgi apparatus play a critical role in regulating signal transmission to the nucleus. Recent experiments have shown that appropriate positioning of these organelles within the intracellular space is critical for effective signal regulation. To understand the mechanism behind this observation, we consider a reaction-diffusion model of an intracellular signaling cascade and investigate the effect on the signaling of intracellular regulation in the form of a small release of phosphorylated signaling protein, kinase, and/or phosphatase. Variational analysis is applied to characterize the most effective regions for the localization of this intracellular regulation. The results demonstrate that signals reaching the nucleus are most effectively regulated by localizing the release of phosphorylated substrate protein and kinase near the nucleus. Phosphatase release, on the other hand, is nearly equally effective throughout the intracellular space. The effectiveness of the intracellular regulation is affected strongly by the characteristics of signal propagation through the cascade. For signals that are amplified as they propagate through the cascade, reactions in the upstream levels of the cascade exhibit much larger sensitivities to regulation by release of phosphorylated substrate protein and kinase than downstream reactions. On the other hand, for signals that decay through the cascade, downstream reactions exhibit larger sensitivity than upstream reactions. For regulation by phosphatase release, all reactions within the cascade show large sensitivity for amplified signals but lose this sensitivity for decaying signals. We use the analysis to develop a simple model of endosome-mediated regulation of cell signaling. The results demonstrate that signal regulation by the modeled endosome is most effective when the endosome is positioned in the vicinity of the nucleus. The present findings may explain at least in part why endosomes in many cell types localize near the nucleus.     

Measurement of Shoulder Range of Motion in Patients with Adhesive Capsulitis Using a Kinect

Range of motion (ROM) measurements are essential for the evaluation for and diagnosis of adhesive capsulitis of the shoulder (AC). However, taking these measurements using a goniometer is inconvenient and sometimes unreliable. The Kinect (Microsoft, Seattle, WA, USA) is gaining attention as a new motion detecting device that is nonintrusive and easy to implement. This study aimed to apply Kinect to measure shoulder ROM in AC; we evaluated its validity by calculating the agreement of the measurements obtained using Kinect with those obtained using goniometer and assessed its utility for the diagnosis of AC. Both shoulders of 15 healthy volunteers and affected shoulders of 12 patients with AC were included in the study. The passive and active ROM of each were measured with a goniometer for flexion, abduction, and external rotation. Their active shoulder motions for each direction were again captured using Kinect and the ROM values were calculated. The agreement between the two measurements was tested with the intraclass correlation coefficient (ICC). Diagnostic performance using the Kinect ROM was evaluated with Cohen’s kappa value. The cutoff values of the limited ROM were determined in the following ways: the same as passive ROM values, reflecting the mean difference, and based on receiver operating characteristic curves. The ICC for flexion/abduction/external rotation between goniometric passive ROM and the Kinect ROM were 0.906/0.942/0.911, while those between active ROMs and the Kinect ROMs were 0.864/0.932/0.925. Cohen’s kappa values were 0.88, 0.88, and 1.0 with the cutoff values in the order above. Measurements of the shoulder ROM using Kinect show excellent agreement with those taken using a goniometer. These results indicate that the Kinect can be used to measure shoulder ROM and to diagnose AC as an alternative to goniometer.     

Regulation of c-Myc Expression by Ahnak Promotes Induced Pluripotent Stem Cell Generation

We have previously reported that Ahnak-mediated TGFβ signaling leads to down-regulation of c-Myc expression. Here, we show that inhibition of Ahnak can promote generation of induced pluripotent stem cells (iPSC) via up-regulation of endogenous c-Myc. Consistent with the c-Myc inhibitory role of Ahnak, mouse embryonic fibroblasts from Ahnak-deficient mouse (Ahnak^−/− MEF) show an increased level of c-Myc expression compared with wild type MEF. Generation of iPSC with just three of the four Yamanaka factors, Oct4, Sox2, and Klf4 (hereafter 3F), was significantly enhanced in Ahnak^−/− MEF. Similar results were obtained when Ahnak-specific shRNA was applied to wild type MEF. Of note, expressionof Ahnak was significantly induced during the formation of embryoid bodies from embryonic stem cells, suggesting that Ahnak-mediated c-Myc inhibition is involved in embryoid body formation and the initial differentiation of pluripotent stem cells. The iPSC from 3F-infected Ahnak^−/− MEF cells (Ahnak^−/−-iPSC-3F) showed expression of all stem cell markers examined and the capability to form three primary germ layers. Moreover, injection of Ahnak^−/−-iPSC-3F into athymic nude mice led to development of teratoma containing tissues from all three primary germ layers, indicating that iPSC from Ahnak^−/− MEF are bona fide pluripotent stem cells. Taken together, these data provide evidence for a new role for Ahnak in cell fate determination during development and suggest that manipulation of Ahnak and the associated signaling pathway may provide a means to regulate iPSC generation.     

Optimal Sequence of Irinotecan and Oxaliplatin-Based Regimens in Metastatic Colorectal Cancer: A Population-Based Observational Study

The optimal sequence of irinotecan and oxaliplatin-based regimens for metastatic colorectal cancer remains unclear. We conducted a population-based observational study by retrospectively reviewing records from Taiwan’s National Health Insurance Research Database to explore this issue. Patients aged ≥20 years with metastatic colorectal cancer newly diagnosed between 2004 and 2008 (n = 9490) were enrolled in current study. Among these 9490 patients, 3895 patients (41.04%) did not receive any chemotherapy within the first three months after catastrophic illness registration. Patients who received best supportive care were older and had higher Charlson comorbidity indexes and incidences of comorbidities than those who received irinotecan-based regimens, oxaliplatin-based regimens, and 5-fluorouracil/capecitabine alone. Patients who received irinotecan followed by oxaliplatin-based regimens and those who received the reverse sequence were further stratified into arm A (n = 542) and arm B (n = 1156), respectively. The median first time to next treatment was not significantly different between arm A and arm B (210 days vs. 196 days; p = 0.17). However, the median second time to next treatment was longer in arm A than in arm B (155 days vs. 123 days; p = 0.006), which translated into a better overall survival (487 days vs. 454 days; p = 0.02). The crossover rate was higher in arm A than in arm B (47.84% vs. 41.61%; p<0.001). Multivariate Cox regression analyses showed that overall survival was comparable between the two chemotherapy sequences (p = 0.27). Our study suggested that irinotecan followed by oxaliplatin-based regimens might be a better chemotherapy treatment option for metastatic colorectal cancer than the reverse sequence given the higher crossover rate and potential overall survival benefit.     

Tumorigenic transformation of NIH 3T3 cells by the autocrine synthesis of transforming growth factor alpha

A variety of cancer cells overexpress transforming growth factor alpha (TGF alpha), a mitogenic peptide. A cDNA sequence coding for the full-length human TGF alpha precursor protein was subcloned into a retroviral expression vector and introduced into clone 7 NIH 3T3 cells, which have low numbers of endogenous epidermal growth factor receptors (EGFRs). The autocrine synthesis of TGF alpha by these cells resulted in their focal transformation. In contrast, control NIH 3T3 cells treated in a paracrine manner with exogenous, saturating concentrations of the mature form of TGF alpha, though stimulated to divide, remained morphologically untransformed. The addition of saturating quantities of soluble, mature TGF alpha to NIH 3T3 cells expressing the transferred TGF alpha gene actually suppressed their growth and focal transformation. The transformation induced by the TGF alpha gene remained an EGFR-dependent process, since the degree of transformation was correlated with EGFR expression in NIH 3T3 cells and since NR6 cells, which are Swiss 3T3 cells devoid of endogenous EGFRs, were transformed by the TGF alpha vector only when exogenous EGFR genes were also introduced. When inoculated into nude mice, the TGF alpha-expressing cells rapidly gave rise to tumors that grew progressively, whereas control cells did not form tumors. We conclude that in certain circumstances autocrine TGF alpha can be more oncogenic than paracrine and that paracrine TGF alpha can suppress this effect.