The chaperone action of bovine milk αS1- and αS2-caseins and their associated form αS-casein

α_S-Casein, the major milk protein, comprises α_S1- and α_S2-casein and acts as a molecular chaperone, stabilizing an array of stressed target proteins against precipitation. Here, we report that α_S-casein acts in a similar manner to the unrelated small heat-shock proteins (sHsps) and clusterin in that it does not preserve the activity of stressed target enzymes. However, in contrast to sHsps and clusterin, α-casein does not bind target proteins in a state that facilitates refolding by Hsp70. α_S-Casein was also separated into α- and α-casein, and the chaperone abilities of each of these proteins were assessed with amorphously aggregating and fibril-forming target proteins. Under reduction stress, all α-casein species exhibited similar chaperone ability, whereas under heat stress, α-casein was a poorer chaperone. Conversely, α_S2-casein was less effective at preventing fibril formation by modified κ-casein, whereas α- and α_S1-casein were comparably potent inhibitors. In the presence of added salt and heat stress, α_S1-, α- and α_S-casein were all significantly less effective. We conclude that α_S1- and α-casein stabilise each other to facilitate optimal chaperone activity of α_S-casein. This work highlights the interdependency of casein proteins for their structural stability.     

Effects of duodenal infusion of free α-linolenic acid on the plasma and milk proteome of lactating dairy cows

This study is an exploratory analysis for understanding the effect of a duodenal infusion of an α-linolenic acid (LNA) on the plasma and milk proteome of lactating dairy cows. Four primiparous Holstein cows were fitted with duodenal cannulas and received 0, 100, 200, 300 and 400 g/day of LNA in a two-treatment crossover design. Blood and milk were collected for determination of protein composition by two-dimensional gel electrophoresis. Alteration of protein spots was detected and identified using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF-TOF MS). Plasma haptoglobin levels, and milk β-casein A2, α_s1-casein variant and albumin, did not differ in cows after infusion of 0, 100, 200 and 300 g/day of LNA, but were increased after the cows received duodenal infusion of 400 g/day of LNA. Western blot analysis of haptoglobin expression in plasma confirmed the alterations in protein expression seen using MS. This study demonstrated that infusion of high doses of LNA by duodenal cannula can result in metabolic stress within the bovine intestine and in changes in milk composition.     

Oleate and linoleate stimulate degradation of β-casein in prolactin-treated HC11 mouse mammary epithelial cells

Although virtually all cells store neutral lipids as cytoplasmic lipid droplets, mammary epithelial cells have developed a specialized function to secrete them as milk fat globules. We have used the mammary epithelial cell line HC11 to evaluate the potential connections between the lipid and protein synthetic pathways. We show that unsaturated fatty acids induce a pronounced proliferation of cytoplasmic lipid droplets and stimulate the synthesis of adipose differentiation-related protein. Unexpectedly, the cellular level of β-casein, accumulated under lactogenic hormone treatment, decreases following treatment of the cells with unsaturated fatty acids. In contrast, saturated fatty acids have no significant effect on either cytoplasmic lipid droplet proliferation or cellular β-casein levels. We demonstrate that the action of unsaturated fatty acids on the level of β-casein is post-translational and requires protein synthesis. We have also observed that proteasome inhibitors potentiate β-casein degradation, indicating that proteasomal activity can destroy some cytosolic protein(s) involved in the process that negatively controls β-casein levels. Finally, lysosome inhibitors block the effect of unsaturated fatty acids on the cellular level of β-casein. Our data thus suggest that the degradation of β-casein occurs via the microautophagic pathway.     

Post-weaning feed efficiency decreased in progeny of higher milk yielding beef cows

Current trends in the beef industry focus on selecting production traits with the purpose of maximizing calf weaning weight; however, such traits may ultimately decrease overall post-weaning productivity. Therefore, the objective of this study was to evaluate the effects of actual milk yield in mature beef cows on their offspring’s dry matter intake (DMI), BW, average daily gain, feed conversion ratio (FCR) and residual feed intake (RFI) during a ~75-day backgrounding feeding trial. A period of 24-h milk production was measured with a modified weigh-suckle-weigh technique using a milking machine. After milking, cows were retrospectively classified as one of three milk yield groups: Lower (6.57±1.21 kg), Moderate (9.02±0.60 kg) or Higher (11.97±1.46 kg). Calves from Moderate and Higher milk yielding dams had greater (P<0.01) BW from day 0 until day 75 at the end of the backgrounding feeding phase; however, day 75 BW were not different (P=0.36) between Lower and Moderate calves. Body weight gain was greater (P=0.05) for Lower and Moderate calves from the day 0 BW to day 35 BW compared with Higher calves. Overall DMI was lower (P=0.03) in offspring from Lower and Moderate cows compared with their Higher milking counterparts. With the decreased DMI, FCR was lower (P=0.03) from day 0 to day 35 in calves from Lower and Moderate milk yielding dams. In addition, overall FCR was lower (P=0.02) in calves from Lower and Moderate milk yielding dams compared with calves from Higher milk yielding dams. However, calving of Lower milk yielding dams had an increased (P=0.04) efficiency from a negative RFI value compared with calves from Moderate and Higher milking dams. Results from this study suggest that increased milk production in beef cows decreases feed efficiency during a 75-day post-weaning, backgrounding period of progeny.     

The effects of the bont tick, Amblyomma hebraeum, on milk production of Sanga and Sanga x Brahman cattle

Abstract. The effects of adults of the bont tick, Amblyomma hebraeum on the milk production of Sanga and Sanga x zebu (Brahman) cattle were measured over a period of 11 weeks in the lowveld of Zimbabwe in the summer of 1986. Four groups of lactating cows, consisting of two breeds, each divided into a high and low tick treatment, were exposed to very low or high challenges of ticks and their milk production measured by weighing their calves before and after suckling. The liveweight gains (LWG) of the calves were also measured.
Tick burdens on the infested groups averaged around fourteen engorging females of A.hebraeum per day, which amounted to infestations of about 150 adult ticks. That is greater than most observed field infestations. This caused no significant reduction in milk yield or calf growth over the whole period, provided the teats of the dams had not been damaged by ticks. Mismothering occurred when teats were damaged. No breed differences were observed so all data was pooled for further analysis. Average calf LWGs of the high tick groups were reduced by 2.2kg (P < 0.01) during one 4-week period but overall the 3.9 kg difference in LWG of the tick treatment groups was not quite significant (P < 0.10). Although there was a poor relationship between tick numbers and reduced milk yield or calf LWG, the effects were always in the direction expected. The effects averaged 6 ± lOg reduction of milk and 2.6 ± 1.8g loss of LWG of calves for every female tick that engorged. It was concluded that milk production is not an important consideration when estimating the losses in production caused by A.hebraeum on Brahman x Sanga or Sanga breeds of cattle. Losses due to teat or udder damage could be much more important and need to be quantified.     

Deletion of one of the duplicated Hsp70 genes causes hereditary myopathy of diaphragmatic muscles in Holstein-Friesian cattle

Heat-shock protein 70 (Hsp70) is a major chaperone that folds protein and prevents aggregation. The Hsp70 family contains both constitutive and stress-inducible forms. In humans, two of the inducible Hsp70 genes are located within the human major histocompatibility complex (MHC) on 6p21.3, as a duplicated locus, 12 kb apart from each other. We report that loss of one of the duplicated Hsp70 genes, the bovine homologue within the bovine MHC, is responsible for hereditary myopathy of diaphragmatic muscles (HMDM) in Holstein-Friesian cattle. Although the remaining Hsp70 gene is intact, Hsp70 protein levels are dramatically decreased in affected cattle. In normal diaphragmatic muscle, Hsp70 binds several proteins involved in energy metabolism including glycogen phosphorylase (PYGM). Immunohistochemical staining indicated that PYGM accumulated in the HMDM-specific core-like structures in affected cattle. Misfolding of energy-related proteins due to Hsp70 deficiency might lead to protein aggregation and muscle fibre degeneration.     

Minimizing cows’ stress when calves were early weaned using the two-step method with nose flaps

Early weaning may be used in beef cattle production to improve reproduction rates in range conditions. However, weaning causes a stress response in cows, which may be especially strong in early weaning management, as the bond between the cow and the calf is still strong. We hypothesized that weaning calves in two steps, with the aid of anti-sucking devices (nose flaps) would reduce the behavioural stress response in the cows separated from their calves 2 months after parturition. We compared the behaviour frequency and weight change in cows that were weaned abruptly, by separation of the calf on day 0 of the study, or in two steps, consisting of the use of anti-sucking nose flaps for 5 days before permanent separation; a third group was not weaned to serve as control. Thirty-six crossbred multiparous Aberdeen Angus×Hereford cows and their calves (n=12/treatment) were managed in three paddocks with similar pasture availability, with four dyads from each treatment per paddock. Cows’ behaviour was observed by direct visual instantaneous sampling, at 10 min intervals from days −3 to 11. Weaning the calves in two steps clearly attenuated the behavioural stress response observed in abruptly weaned cows, which included reductions in grazing and lying, and increases in pacing, walking and vocalizing. Our results corroborate those previously shown for cows nursing older calves, and indicate that step weaning can reduce the behavioural stress response of cows at weaning, even when the calf is weaned shortly after birth, when the bond between the cow and calf is still very strong.     

Effects of the processing methods of corn grain and soybean meal on milk protein expression profiles in dairy cows

A proteomic approach was used to investigate the effects of the processing method of corn grain and soybean meal on the milk protein expression profile in lactating dairy cows. A total of 12 multiparous Holstein dairy cows were used in a 4×4 Latin square design with a 2×2 factorial arrangement. The primary factors examined were corn (finely ground (FGC) v. steam-flaked (SFC)) and soybean meal (solvent-extracted (SSBM) v. heat-treated (HSBM)), which were used to formulate four diets with the same basal ingredient: 27% FGC and 9% SSBM; 27% SFC and 9% SSBM; 27% FGC and 9% HSBM; and 27% SFC and 9% HSBM. Each period lasted for 21 days. Milk samples were collected on days 18, 19 and 20 of each period. Changes in the milk proteins were assessed by two-dimensional (2D) electrophoresis and ImageMaster 2D Platinum 6.0 software. A total of 13 spots displayed variations in protein spot abundance according to the statistical analysis. These spots were identified by a matrix-assisted laser desorption/ionization-time of flight/time of flight MS. According to the gels, the relative abundance of α_s2-casein (CN) fragments was higher in the cows fed the SFC-HSBM than that for SFC-SSBM, whereas β-CN, α-lactalbumin and zinc-alpha-2-glycoprotein fragments were down-regulated in HSBM-fed cows. The relative decrease of β-CN expression was validated by western blot and agreed with the MS data. These results suggested that the method used to process soybean meal modified the synthesis and secretion of milk proteins in lactating dairy cows’ mammary glands.     

Protein deprivation attenuates Hsp expression in fat tissue

For ruminants, dietary protein is the first limiting component to the utilization of low-quality forage. Throughout gestation, low-protein intake may result in prenatal programming that causes various metabolic disturbances and physiological modulations to dams and their developing embryos. We studied the effect of long-term low-protein diet (LPD) on physiological, biochemical, and molecular parameters of the energy status in gestating beef cows. LPD resulted in significant reductions in feed intake and heart rate and promoted a negative retained energy status already after 3 weeks. Elevated levels of plasma creatinine and non-esterified fatty acids indicate endogenous degradation of fat and protein as a response to the demands in energy and nitrogen. Increasing levels of β-hydroxybutyrate confirmed the negative energy status obtained by the physiological measurements. At the molecular level, subcutaneous fat, Hsp90, Hsp70, and proteasome subunits decreased significantly after 3 months on LPD, in parallel with an increase of adipocyte fatty acid-binding protein. These results may indicate a decrease in turn-over of proteins, at the cost of induced lipolysis, and suggest that the response to protein deprivation, when examined in an energy-storing tissue, includes downregulation of the constitutive heat shock proteins involved in the protein degradation pathway of energy production and upregulation of tissue-specific genes such as those involved in energy production from fat degradation.     

Differential abundance of IGF1, bile acids,and the genes involved in their signaling in the dominant follicle microenvironment of lactating cows and nulliparous heifers

It is well documented that incidence of fertility problems is high in lactating cows but not in heifers of the same genetic merit. Understanding the metabolic and molecular differences between fertile heifers and relatively infertile lactating cows will help us understand the pathogenesis of infertility in dairy cows. Follicular waves in lactating cows (30–50 days in milk; n = 12) and heifers (n = 10) were synchronized by ultrasound-guided follicle ablation. Follicular fluid and granulosa cells of the dominant follicle were collected by ultrasound-guided aspiration along with blood sampling on Day 6 after synchronization. Dominant and subordinate follicles were larger in lactating cows than in heifers. Metabolic stress in lactating cows was evidenced by lower glucose and higher ß-hydroxy butyric acid compared with heifers. Insulin-like growth factor 1 signaling was reduced in the dominant follicle in lactating cows through reduced insulin-like growth factor 1 concentrations in plasma and follicular fluid of the dominant follicle, and reduced expression of pregnancy-associated plasma protein A (PAPPA) in their granulosa cells. We also found increased levels of total bile acids in the follicular fluid of the dominant follicle of lactating cows compared with heifers. Granulosa cells of the dominant follicle had higher expression of SLC10A2 and GPBAR1 (bile acid transporter and receptor, respectively) in lactating cows. These novel data are indicative of increased bile acid signaling within the dominant follicles of lactating cows compared with heifers. Overall, we demonstrate in the present study the metabolic, endocrine, and molecular differences within the microenvironment of the dominant follicles in lactating cows and heifers. These differences in follicular microenvironment may contribute toward abnormal ovarian function in lactating dairy cows.     

The use of embryo transfer in the field for increased calf crops in beef and dairy cattle

Non-surgical transfer of one embryo to 63 previously synchronized inseminated recipients was performed on farms to induce twinning in beef and dairy cattle. All the transfers were done by technicians of A.I. centers. After calving, a twinning rate of 44.4% was achieved with no differences between beef Charolais heifers (45.4%), lactating Normande cows (42.8%) and dairy Friesian cows (45.4%). Compared with controls, the calving crop after a three-breeding-cycle period was significantly higher with recipients: 1.16 calf per treated recipient vs. 0.83 calf per control animal. It would seem that the possibility of obtaining about one-third more calves with embryo transfer could be of economical interest to increase meat production from cattle herds.     

Impact of longevity on greenhouse gas emissions and profitability of individual dairy cows analysed with different system boundaries

Dairy production systems are often criticized as being major emitters of greenhouse gases (GHG). In this context, the extension of the length of the productive life of dairy cows is gaining interest as a potential GHG mitigation option. In the present study, we investigated cow and system GHG emission intensity and profitability based on data from 30 dairy cows of different productive lifetime fed either no or limited amounts of concentrate. Detailed information concerning productivity, feeding and individual enteric methane emissions of the individuals was available from a controlled experiment and herd book databases. A simplified GHG balance was calculated for each animal based on the milk produced at the time of the experiment and for their entire lifetime milk production. For the lifetime production, we also included the emissions arising from potential beef produced by fattening the offspring of the dairy cows. This accounted for the effect that changes in the length of productive life will affect the replacement rate and thus the number of calves that can be used for beef production. Profitability was assessed by calculating revenues and full economic costs for the cows in the data set. Both emission intensity and profitability were most favourable in cows with long productive life, whereas cows that had not finished their first lactation performed particularly unfavourably with regard to their emissions per unit of product and rearing costs were mostly not repaid. Including the potential beef production, GHG emissions in relation to total production of animal protein also decreased with age, but the overall variability was greater, as the individual cow history (lifetime milk yield, twin births, stillbirths, etc.) added further sources of variation. The present results show that increasing the length of productive life of dairy cows is a viable way to reduce the climate impact and to improve profitability of dairy production.     

Effect of a single growth hormone (rbST) treatment at breeding on conception rates and pregnancy retention in dairy and beef cattle

Initiation of long-term treatment with rbST (Posilac, Monsanto, St. Louis, MO) coincident with first insemination increased pregnancy rates in dairy cattle, but neither the efficacy of using only the initial injection, nor its effects on retention of pregnancy are known. Lactating dairy cows, dairy heifers, and lactating beef cows were assigned at random to treatment (rbST) or control. Dairy cows, dairy heifers, and beef cows received 500 mg rbST (n = 48, 35, 137 inseminations, respectively) at artificial insemination or were left untreated (n = 62, 33, 130 inseminations, respectively). Pregnancy was diagnosed by ultrasonography at 28-36 days. Treatment with rbST at insemination improved conception rates in dairy cows (60.4% versus 40.3%; P < 0.05), but not in dairy heifers or beef cows. Conception rates did not differ in dairy cows at < or =100 days in milk (DIM), but were improved in cows treated with rbST after 100 DIM (64.3% versus 25.8%; P < 0.05). Retention of pregnancy to approximately 60 days and sizes of CL, diameter of follicles > or =5 mm, and crown-rump lengths of embryos were not affected by treatment. The second objective was to examine the effects of rbST at insemination on birth weight and post-natal calf growth in beef cows. However, birth and weaning weights of beef calves were not affected by treatment. In conclusion, a single treatment with rbST at insemination increased conception rates in dairy cows, specifically in those >100 DIM.     

Characterisation of the <Emphasis Type="Italic">Plasmodium falciparum</Emphasis> Hsp70–Hsp90 organising protein (PfHop)

Malaria is caused by Plasmodium species, whose transmission to vertebrate hosts is facilitated by mosquito vectors. The transition from the cold blooded mosquito vector to the host represents physiological stress to the parasite, and additionally malaria blood stage infection is characterised by intense fever periods. In recent years, it has become clear that heat shock proteins play an essential role during the parasite's life cycle. Plasmodium falciparum expresses two prominent heat shock proteins: heat shock protein 70 (PfHsp70) and heat shock protein 90 (PfHsp90). Both of these proteins have been implicated in the development and pathogenesis of malaria. In eukaryotes, Hsp70 and Hsp90 proteins are functionally linked by an essential adaptor protein known as the Hsp70–Hsp90 organising protein (Hop). In this study, recombinant P. falciparum Hop (PfHop) was heterologously produced in E. coli and purified by nickel affinity chromatography. Using specific anti-PfHop antisera, the expression and localisation of PfHop in P. falciparum was investigated. PfHop was shown to co-localise with PfHsp70 and PfHsp90 in parasites at the trophozoite stage. Gel filtration and co-immunoprecipitation experiments suggested that PfHop was present in a complex together with PfHsp70 and PfHsp90. The association of PfHop with both PfHsp70 and PfHsp90 suggests that this protein may mediate the functional interaction between the two chaperones.     

Expression and regulation of hFIX minigene and cDNA driven by β-casein gene in mouse mammary gland

Mammary gland specific expression vectors for human clotting factor IX (hFIX) and LacZ reporter gene driven by bovine β-casein gene were constructed. Vectors were packaged by stearylamine (SA) liposome and were transferred to lactating mice via tail vein. Both hFIX and Lac2 gene could be expressed in the mammary gland of the treated mice. The highest production of hFIX protein was 80.28 ng per mL milk, and more than 85% of hFIX protein appeared to be γ-carboxylation and biologically active. The results suggested that the 2.0 kb sequence of β-casein gene including promoter, exon 1 was effective to drive hFIX gene expression in mammary gland and intron 1 of β-casein gene had an effect on the tissue specific expression. The expression level in mouse milk injected with hFIX minigene vector containing hFIX endogenous intron 1 was increased by above 3 times of that injected with hFIX cDNA vector. Project supported by the State High Technology Development Program and Shanghai Science and Technology Commission.     

Promoter variants at AP2 box region of Hsp70.1 affect thermal stress response and milk production traits in Frieswal cross bred cattle

Heat shock proteins (Hsp) are known to play major role in protection of cells from thermal stress. Nucleotide polymorphisms within the promoter of Hsp affect degree of expression and inducibility of Hsp mRNA. The present study aimed to investigate the effect of polymorphism within promoter region on the cellular expression of Hsp70.1 mRNA and association of identified polymorphisms with the physiological parameters during summer stress and milk production traits in dairy cattle. Two hundred Frieswal cows were genotyped using double PCR-RFLP to identify deletion of cytosine within the Hsp70.1 promoter AP2 box at base position 895. Homozygous wild type genotypes (CC) were found in lower frequency (39.29, n = 78) than heterozygous cytosine deletion mutant genotypes (C −) (60.71, n = 122). In the observed physiological parameters (rectal temperature, respiration rate and heat tolerance coefficient), cows that were homozygous wild types had better significant (P < 0.05) summer tolerance than the heterozygous deletion genotypes. Cytosine deletion mutation in the promoter region negatively affected (P < 0.01) the expression of Hsp70.1 mRNA in peripheral bovine mononuclear cells (PBMC) subjected to in vitro heat stress. Further association of observed polymorphism with the milk production traits was significant as the heterozygous cytosine deletion cows had lower total milk yield, peak yield, yield at 300 days, protein% (P < 0.01) and fat% (P < 0.05) than the native wild type promoter cows. The results from the present study suggest that the promoter region of bovine hsp70.1 gene is polymorphic and may be useful in selection of dairy cows for relatively better thermotolerance and higher milk production.     

Comparison of milk produced by cows cloned by nuclear transfer with milk from non-cloned cows

Cloning technologies, including embryo splitting and nuclear transfer, were introduced into dairy cattle breeding in the early 1980s. With the recent worldwide attention on the cloning of sheep ("Dolly") and cows ("Gene"), the potential food safety concerns for food products derived from cloned animals needs to be addressed. There has been no study of the composition of milk produced by cloned cows. In this preliminary study, we evaluated the composition of milk from 15 lactating non-embryonic cell cloned cows and six non-cloned lactating cows over a single season. The cloned cows came from five unique genetic lines and three distinct breeds. Milk samples were analyzed for total solids, fat, fatty acid profile, lactose, protein and compared to non-cloned and literature values. Gross chemical composition of milk from cloned cows was similar to that of the non-cloned cows and literature values. Our results lead us to conclude that there are no obvious differences in milk composition produced from cloned cows compared to non-cloned cows.     

Canola Oil in Lactating Dairy Cow Diets Reduces Milk Saturated Fatty Acids and Improves Its Omega-3 and Oleic Fatty Acid Content

To produce milk that is healthier for human consumption, the present study evaluated the effect of including canola oil in the diet of dairy cows on milk production and composition as well as the nutritional quality of this milk fat. Eighteen Holstein cows with an average daily milk yield of 22 (± 4) kg/d in the middle stage of lactation were used. The cows were distributed in 6 contemporary 3x3 Latin squares consisting of 3 periods and 3 treatments: control diet (without oil), 3% inclusion of canola oil in the diet and 6% inclusion of canola oil in the diet (dry matter basis). The inclusion of 6% canola oil in the diet of lactating cows linearly reduced the milk yield by 2.51 kg/d, short-chain fatty acids (FA) by 41.42%, medium chain FA by 27.32%, saturated FA by 20.24%, saturated/unsaturated FA ratio by 39.20%, omega-6/omega-3 ratio by 39.45%, and atherogenicity index by 48.36% compared with the control treatment. Moreover, with the 6% inclusion of canola oil in the diet of cows, there was an increase in the concentration of long chain FA by 45.91%, unsaturated FA by 34.08%, monounsaturated FA by 40.37%, polyunsaturated FA by 17.88%, milk concentration of omega-3 by 115%, rumenic acid (CLA) by 16.50%, oleic acid by 44.87% and h/H milk index by 94.44% compared with the control treatment. Thus, the inclusion of canola oil in the diet of lactating dairy cows makes the milk fatty acid profile nutritionally healthier for the human diet; however, the lactating performance of dairy cows is reduce.     

Nmi interacts with Hsp105β and enhances the Hsp105β-mediated Hsp70 expression

The mammalian stress protein Hsp105α is expressed constitutively and is further induced under stress conditions, whereas the alternative spliced form, Hsp105β is only expressed during mild heat shock. We previously reported that Hsp105α is localized mainly in the cytoplasm, whereas Hsp105β is localized in the nucleus. Consistent with the different localization of these proteins, Hsp105β but not Hsp105α induces the expression of the major stress protein Hsp70. We here identified N-myc and Stat interactor (Nmi), as an Hsp105β-binding protein by yeast two-hybrid screening. Immunoprecipitation and pull-down assay showed that Nmi interacts with Hsp105β in vivo and in vitro. Luciferase reporter gene assay and Western blotting showed that Nmi enhanced both the Hsp105β-induced phosphorylation of Stat3 and the Hsp105β-induced activation of the hsp70 promoter in a manner that is dependent on the Stat3-binding site, which results in an increase in Hsp70 protein levels. Most importantly, mild heat shock-induced Hsp70 expression, which is dependent on Hsp105β, is suppressed by knockdown of endogenous Nmi. These results suggest that Nmi has a role as a positive regulator of Hsp105β-mediated hsp70 gene expression along the Stat3 signaling pathway.