Hg1, novel peptide inhibitor specific for Kv1.3 channels from first scorpion Kunitz-type potassium channel toxin family.

The potassium channel Kv1.3 is an attractive pharmacological target for autoimmune diseases. Specific peptide inhibitors are key prospects for diagnosing and treating these diseases. Here, we identified the first scorpion Kunitz-type potassium channel toxin family with three groups and seven members. In addition to their function as trypsin inhibitors with dissociation constants of 140 nM for recombinant LmKTT-1a, 160 nM for LmKTT-1b, 124 nM for LmKTT-1c, 136 nM for BmKTT-1, 420 nM for BmKTT-2, 760 nM for BmKTT-3, and 107 nM for Hg1, all seven recombinant scorpion Kunitz-type toxins could block the Kv1.3 channel. Electrophysiological experiments showed that six of seven scorpion toxins inhibited ~50-80% of Kv1.3 channel currents at a concentration of 1 µM. The exception was rBmKTT-3, which had weak activity. The IC(50) values of rBmKTT-1, rBmKTT-2, and rHg1 for Kv1.3 channels were ~129.7, 371.3, and 6.2 nM, respectively. Further pharmacological experiments indicated that rHg1 was a highly selective Kv1.3 channel inhibitor with weak affinity for other potassium channels. Different from classical Kunitz-type potassium channel toxins with N-terminal regions as the channel-interacting interfaces, the channel-interacting interface of Hg1 was in the C-terminal region. In conclusion, these findings describe the first scorpion Kunitz-type potassium channel toxin family, of which a novel inhibitor, Hg1, is specific for Kv1.3 channels. Their structural and functional diversity strongly suggest that Kunitz-type toxins are a new source to screen and design potential peptides for diagnosing and treating Kv1.3-mediated autoimmune diseases.

Distributional Response of the Rare and Endangered Tree Species Abies chensiensis to Climate Change in East Asia.

Globally, increasing temperatures due to climate change have severely affected natural ecosystems in several regions of the world; however, the impact on the alpine plant may be particularly profound, further raising the risk of extinction for rare and endangered alpine plants. To identify how alpine species have responded to past climate change and to predict the potential geographic distribution of species under future climate change, we investigated the distribution records of A. chensiensis, an endangered alpine plant in the Qinling Mountains listed in the Red List. In this study, the optimized MaxEnt model was used to analyse the key environmental variables related to the distribution of A. chensiensis based on 93 wild distribution records and six environmental variables. The potential distribution areas of A. chensiensis in the last interglacial (LIG), the last glacial maximum (LGM), the current period, and the 2050s and 2070s were simulated. Our results showed that temperature is critical to the distribution of A. chensiensis, with the mean temperature of the coldest quarter being the most important climatic factor affecting the distribution of this species. In addition, ecological niche modeling analysis showed that the A. chensiensis distribution area in the last interglacial experiencing population expansion and, during the last glacial maximum occurring, a population contraction. Under the emission scenarios in the 2050s and 2070s, the suitable distribution area would contract significantly, and the migration routes of the centroids tended to migrate toward the southern high-altitude mountains, suggesting a strong response from the A. chensiensis distribution to climate change. Collectively, the results of this study provide a comprehensive and multidimensional perspective on the geographic distribution pattern and history of population dynamics for the endemic, rare, and endangered species, A. chensiensis, and it underscores the significant impact of geological and climatic changes on the geographic pattern of alpine species populations.

Spatial patterns and interspecific relationships of two dominant cushion plants at three elevations on the Kunlun Mountain, China.

One of the most important ecological processes is the formation of interspecific relationships in relation to spatial patterns among alpine cushion plants in extreme environmental habitats. However, such relationships remain poorly understood. Here, we examined the spatial patterns of alpine cushion plants along an altitudinal gradient of environmental severity and the interspecific relationship between two cushion species (Thylacospermum caespitosum and Androsace tangulashanensis) on the eastern Kunlun Mountain of China. Our results showed that the two species were highly aggregated within a distance of 2.5-5 m at the mid (S2) altitude, whereas they were randomly distributed at the low (S1) and high (S3) altitudes. A positive spatial interaction between the two species was observed over shorter distances at the mid (S2) altitude, and the spatial patterns were related to the size of individuals of the two species. Moreover, the impact of A. tangulashanensis on T. caespitosum (RIIT. caespitosum) was negative in all the study plots, and a positive impact of T. caespitosum on A. tangulashanensis (RIIA. tangulashanensis) was only observed at the mid (S2) altitude. Together, these results demonstrated that the spatial patterns of these two cushions varied with environmental severity, since the outcome of the interactions were different, to some extent, at the three altitudes. Plant size is the main factor affecting the spatial correlation and interspecific relationship between two cushions. Therefore, its potential influence should be considered when discussing interspecific relationships among cushions and their community construction at small scales in alpine ecosystems.

Thylacospermum caespitosum population structure and cushion species community diversity along an altitudinal gradient.

As alpine plants, cushion species are particularly susceptible to environment changes. Thus, understanding population structure and community diversity variation of cushion plants along elevational gradients is crucial for estimating their response to predicted climate changes. In this study, Thylacospermum caespitosum populations from three elevations (low, medium, and high) in three climate zones of China (the Kunlun, Qilian, and Tianshan Mountains) were selected to evaluate the effect of elevation on the structure of T. caespitosum populations and species diversity of cushion communities. Results showed that elevation substantially influenced T. caespitosum populations (size structure, density, and death rate), as well as richness (α-diversity) and microhabitat species pool (species pool) of cushion communities. In the low elevations, T. caespitosum populations were in decline due to a lower ratio of small plants and higher mortality compared with populations at medium and high elevations. The α-diversity and species pool in cushion communities were significantly increased with decreased elevation, but the importance value of T. caespitosum decreased accordingly. Moreover, there was a significant positive correlation between elevation and relative importance value (the importance of one species in the community) of T. caespitosum (r = 0.883; P < 0.01). Elevation was significantly negatively correlated with the mortality rate of T. caespitosum (r = - 0.855; P < 0.01), α-diversity (r = - 0.933; P < 0.001), and species pool (r = - 0.885; P < 0.01). The declining characters of T. caespitosum population structure were obvious in low elevation populations. This decline may directly or indirectly relate to environmental change. Effects of elevation can provide an early indication of range contractions and population declines of cushion species with future climate warming. We call for more mechanistic studies of climate change impacts on cushion populations, particularly in alpine systems near the snow line.