The MAPK homolog, Smk1, promotes assembly of the glucan layer of the spore wall in S. cerevisiae.

Smk1 is a MAPK homolog in the yeast Saccharomyces cerevisiae that controls the postmeiotic program of spore wall assembly. During this program, haploid cells are surrounded by a layer of mannan and then a layer of glucan. These inner layers of the spore wall resemble the vegetative cell wall. Next, the outer layers consisting of chitin/chitosan and then dityrosine are assembled. The outer layers are spore-specific and provide protection against environmental stressors. Smk1 is required for the proper assembly of spore walls. However, the protective properties of the outer layers have limited our understanding of how Smk1 controls this morphogenetic program. Mutants lacking the chitin deacetylases, Cda1 and Cda2, form spores that lack the outer layers of the spore wall. In this study, cda1,2∆ cells were used to demonstrate that Smk1 promotes deposition of the glucan layer of the spore wall through the partially redundant glucan synthases Gsc2 and Fks3. Although Gsc2 is localized to sites of spore wall assembly in the wild type, it is mislocalized in the mother cell cytoplasm in the smk1∆ mutant. These findings suggest that Smk1 controls assembly of the spore wall by regulating the localization of Gsc2 during sporogenesis.

Isc10, an inhibitor of the Smk1 MAPK, prevents activation loop autophosphorylation and substrate phosphorylation through separate mechanisms.

Many eukaryotic protein kinases are activated by the intramolecular autophosphorylation of activation loop residues. Smk1 is a meiosis-specific mitogen-activated protein kinase (MAPK) in yeast that autophosphorylates its activation loop tyrosine and thereby upregulates catalytic output. This reaction is controlled by an inhibitor, Isc10, that binds the MAPK during meiosis I and an activator, Ssp2, that binds Smk1/Isc10 during meiosis II. Upon completion of the meiotic divisions, Isc10 is degraded, and Smk1 undergoes autophosphorylation to generate the high activity form of the MAPK that controls spore formation. How Isc10 inhibits Smk1 is not clear. Here, we use a bacterial coexpression/reconstitution system to define a domain in the carboxy-terminal half of Isc10 that specifically inhibits Smk1 autophosphorylation. Nevertheless, Smk1 bound by this domain is able to phosphorylate other substrates, and it phosphorylates the amino-terminal half of Isc10 on serine 97. In turn, the phosphorylated motif in Isc10 inhibits the Smk1 active site. These data show that Isc10 inhibits autophosphorylation and the phosphorylation of substrates by separate mechanisms. Furthermore, we demonstrate Isc10 can inhibit the autophosphorylation of the mammalian intestinal cell kinase ICK1 (also known as CILK1), suggesting a conserved mechanism of action. These findings define a novel class of developmentally regulated molecules that prevent the self-activation of MAPKs and MAPK-like enzymes.

Meiotic commitment: More than a transcriptional switch.

Commitment to cellular differentiation programs can be controlled by self-activating transcription factors that trigger the expression of cell-type-specific genes. A new study shows that, although commitment to meiosis in yeast is controlled in this manner, additional signaling interactions promote the committed state.

Isc10, an Inhibitor That Links the Anaphase-Promoting Complex to a Meiosis-Specific Mitogen-Activated Protein Kinase.

Smk1 is a meiosis-specific mitogen-activated protein kinase (MAPK) in yeast that controls spore differentiation. It is activated by a MAPK binding protein, Ssp2, upon completion of the meiotic divisions. The activation of Smk1 by Ssp2 is positively regulated by a meiosis-specific coactivator of the anaphase promoting complex (APC/C) E3 ubiquitin ligase, Ama1. Here, we identify Isc10 as an inhibitor that links APC/CAma1 to Smk1 activation. Isc10 and Smk1 form an inhibited complex during meiosis I (MI). Ssp2 is produced later in the program, and it forms a ternary complex with Isc10 and Smk1 during MII that is poised for activation. Upon completion of MII, Isc10 is ubiquitylated and degraded in an AMA1-dependent manner, thereby triggering the activation of Smk1 by Ssp2. Mutations that caused Ssp2 to be produced before MII, or isc10Δ mutations, modestly reduced the efficiency of spore differentiation whereas spores were nearly absent in the double mutant. These findings define a pathway that couples spore differentiation to the G0-like phase of the cell cycle.

Estimation versus falsification approaches in sport and exercise science.

There has been a recent resurgence in debate about methods for statistical inference in science. The debate addresses statistical concepts and their impact on the value and meaning of analyses' outcomes. In contrast, philosophical underpinnings of approaches and the extent to which analytical tools match philosophical goals of the scientific method have received less attention. This short piece considers application of the scientific method to "what-is-the-influence-of x-on-y" type questions characteristic of sport and exercise science. We consider applications and interpretations of estimation versus falsification based statistical approaches and their value in addressing how much x influences y, and in measurement error and method agreement settings. We compare estimation using magnitude based inference (MBI) with falsification using null hypothesis significance testing (NHST), and highlight the limited value both of falsification and NHST to address problems in sport and exercise science. We recommend adopting an estimation approach, expressing the uncertainty of effects of x on y, and their practical/clinical value against pre-determined effect magnitudes using MBI.

Considerations for the Scientific Support Process and Applications to Case Studies.

Case studies are vehicles to bridge the gap between science and practice because they provide opportunities to blend observations and interventions that have taken place in real-world environments with scientific rigor. The purpose of this invited commentary is to present considerations for those providing applied sport science support to athletes with the intention of broadcasting this information to the scientific community. The authors present a 4-phased approach (1: athlete overview; 2: needs analysis; 3: intervention planning; and 4: results, evaluation, and conclusion) for scientific support to assist practitioners in the development and implementation of scientific support. These considerations are presented in the form of "performance questions" designed to guide and critically evaluate the scientific support process and aid the transfer of this knowledge through case studies.

RNA Recognition-like Motifs Activate a Mitogen-Activated Protein Kinase.

Smk1 is a mitogen-activated protein kinase (MAPK) family member in the yeast Saccharomyces cerevisiae that controls the postmeiotic program of spore formation. Ssp2 is a meiosis-specific protein that activates Smk1 and triggers the autophosphorylation of its activation loop. A fragment of Ssp2 that is sufficient to activate Smk1 contains two segments that resemble RNA recognition motifs (RRMs). Mutations in either of these motifs eliminated Ssp2's ability to activate Smk1. In contrast, deletions and insertions within the segment linking the RRM-like motifs only partially reduced the activity of Ssp2. Moreover, when the two RRM-like motifs were expressed as separate proteins in bacteria, they activated Smk1. We also find that both motifs can be cross-linked to Smk1 and that at least one of the motifs binds near the ATP-binding pocket of the MAPK. These findings demonstrate that motifs related to RRMs can directly activate protein kinases.

The meiosis-specific Cdc20 family-member Ama1 promotes binding of the Ssp2 activator to the Smk1 MAP kinase.

Smk1 is a meiosis-specific MAP kinase (MAPK) in budding yeast that is required for spore formation. It is localized to prospore membranes (PSMs), the structures that engulf haploid cells during meiosis II (MII). Similar to canonically activated MAPKs, Smk1 is controlled by phosphorylation of its activation-loop threonine (T) and tyrosine (Y). However, activation loop phosphorylation occurs via a noncanonical two-step mechanism in which 1) the cyclin-dependent kinase activating kinase Cak1 phosphorylaytes T207 during MI, and 2) Smk1 autophosphorylates Y209 as MII draws to a close. Autophosphorylation of Y209 and catalytic activity for substrates require Ssp2, a meiosis-specific protein that is translationally repressed until anaphase of MII. Ama1 is a meiosis-specific targeting subunit of the anaphase-promoting complex/cyclosome that regulates multiple steps in meiotic development, including exit from MII. Here, we show that Ama1 activates autophosphorylation of Smk1 on Y209 by promoting formation of the Ssp2/Smk1 complex at PSMs. These findings link meiotic exit to Smk1 activation and spore wall assembly.

Ssp2 Binding Activates the Smk1 Mitogen-Activated Protein Kinase.

Smk1 is a meiosis-specific mitogen-activated protein kinase (MAPK) in Saccharomyces cerevisiae that couples spore morphogenesis to the completion of chromosome segregation. Similar to other MAPKs, Smk1 is controlled by phosphorylation of a threonine (T) and a tyrosine (Y) in its activation loop. However, it is not activated by a dual-specificity MAPK kinase. Instead, T207 in Smk1's activation loop is phosphorylated by the cyclin-dependent kinase (CDK)-activating kinase (Cak1), and Y209 is autophosphorylated in an intramolecular reaction that requires the meiosis-specific protein Ssp2. In this study, we show that Smk1 is catalytically inert unless it is bound by Ssp2. While Ssp2 binding activates Smk1 by a mechanism that is independent of activation loop phosphorylation, binding also triggers autophosphorylation of Y209 in Smk1, which, along with Cak1-mediated phosphorylation of T207, further activates the kinase. Autophosphorylation of Smk1 on Y209 also appears to modify the specificity of the MAPK by suppressing Y kinase and enhancing S/T kinase activity. We also found that the phosphoconsensus motif preference of Ssp2/Smk1 is more extensive than that of other characterized MAPKs. This study therefore defines a novel mechanism of MAPK activation requiring binding of an activator and also shows that MAPKs can be diversified to recognize unique phosphorylation motifs.

Effects of a 12-week aerobic exercise intervention on eating behaviour, food cravings, and 7-day energy intake and energy expenditure in inactive men.

This study examined effects of 12 weeks of moderate-intensity aerobic exercise on eating behaviour, food cravings, and weekly energy intake and expenditure in inactive men. Eleven healthy men (mean ± SD: age, 26 ± 5 years; body mass index, 24.6 ± 3.8 kg·m-2; maximum oxygen uptake, 43.1 ± 7.4 mL·kg-1·min-1) completed the 12-week supervised exercise programme. Body composition, health markers (e.g., blood pressure), eating behaviour, food cravings, and weekly energy intake and expenditure were assessed before and after the exercise intervention. There were no intervention effects on weekly free-living energy intake (p = 0.326, d = -0.12) and expenditure (p = 0.799, d = 0.04) or uncontrolled eating and emotional eating scores (p > 0.05). However, there was a trend with a medium effect size (p = 0.058, d = 0.68) for cognitive restraint to be greater after the exercise intervention. Total food cravings (p = 0.009, d = -1.19) and specific cravings of high-fat foods (p = 0.023, d = -0.90), fast-food fats (p = 0.009, d = -0.71), and carbohydrates/starches (p = 0.009, d = -0.56) decreased from baseline to 12 weeks. Moreover, there was a trend with a large effect size for cravings of sweets (p = 0.052, d = -0.86) to be lower after the exercise intervention. In summary, 12 weeks of moderate-intensity aerobic exercise reduced food cravings and increased cognitive restraint, but these changes were not accompanied by changes in other eating behaviours or weekly energy intake and expenditure. The results indicate the importance of exercising for health improvements even when reductions in body mass are modest.

Effects of a lifestyle intervention on endothelial function in men on long-term androgen deprivation therapy for prostate cancer.

BACKGROUND: Treatment of prostate cancer with androgen deprivation therapy (ADT) is associated with metabolic changes that have been linked to an increase in cardiovascular risk. METHODS: This randomised controlled trial investigated the effects of a 12-week lifestyle intervention that included supervised exercise training and dietary advice on markers of cardiovascular risk in 50 men on long-term ADT recruited to an on-going study investigating the effects of such a lifestyle intervention on quality of life. Participants were randomly allocated to receive the intervention or usual care. Cardiovascular outcomes included endothelial function (flow-mediated dilatation (FMD) of the brachial artery), blood pressure, body composition and serum lipids. Additional outcomes included treadmill walk time and exercise and dietary behaviours. Outcomes were assessed before randomisation (baseline), and 6, 12 and 24 weeks after randomisation. RESULTS: At 12 weeks, the difference in mean relative FMD was 2.2% (95% confidence interval (CI) 0.1-4.3, P=0.04) with an effect size of 0.60 (95% CI <0.01-1.18) favouring the intervention group. Improvements in skeletal muscle mass, treadmill walk time and exercise behaviour also occurred in the intervention group over that duration (P<0.05). At 24 weeks, only the difference in treadmill walk time was maintained. CONCLUSIONS: This study demonstrates that lifestyle changes can improve endothelial function in men on long-term ADT for prostate cancer. The implications for cardiovascular health need further investigation in larger studies over longer duration.

Misuse of "Power" and Other Mechanical Terms in Sport and Exercise Science Research.

Despite the Système International d'Unitès (SI) that was published in 1960, there continues to be widespread misuse of the terms and nomenclature of mechanics in descriptions of exercise performance. Misuse applies principally to failure to distinguish between mass and weight, velocity and speed, and especially the terms "work" and "power." These terms are incorrectly applied across the spectrum from high-intensity short-duration to long-duration endurance exercise. This review identifies these misapplications and proposes solutions. Solutions include adoption of the term "intensity" in descriptions and categorizations of challenge imposed on an individual as they perform exercise, followed by correct use of SI terms and units appropriate to the specific kind of exercise performed. Such adoption must occur by authors and reviewers of sport and exercise research reports to satisfy the principles and practices of science and for the field to advance.

Autophosphorylation of the Smk1 MAPK is spatially and temporally regulated by Ssp2 during meiotic development in yeast.

Smk1 is a meiosis-specific MAPK that controls spore wall morphogenesis in Saccharomyces cerevisiae. Although Smk1 is activated by phosphorylation of the threonine (T) and tyrosine (Y) in its activation loop, it is not phosphorylated by a dual-specificity MAPK kinase. Instead, the T is phosphorylated by the cyclin-dependent kinase (CDK)-activating kinase, Cak1. The Y is autophosphorylated in an intramolecular reaction that requires a meiosis-specific protein named Ssp2. The meiosis-specific CDK-like kinase, Ime2, was previously shown to positively regulate Smk1. Here we show that Ime2 activity is required to induce the translation of SSP2 mRNA at anaphase II. Ssp2 protein is then localized to the prospore membrane, the structure where spore wall assembly takes place. Next the carboxy-terminal portion of Ssp2 forms a complex with Smk1 and stimulates the autophosphorylation of its activation-loop Y residue. These findings link Ime2 to Smk1 activation through Ssp2 and define a developmentally regulated mechanism for activating MAPK at specific locations in the cell.

Effects of an acute bout of aerobic exercise on immediate and subsequent three-day food intake and energy expenditure in active and inactive pre-menopausal women taking oral contraceptives.

UNLABELLED: This study examined the effects of an acute bout of exercise of low-intensity on food intake and energy expenditure over four days in women taking oral contraceptives. Twenty healthy, active (n = 10) and inactive (n = 10) pre-menopausal women taking oral contraceptives completed two conditions (exercise and control), in a randomised, crossover fashion. The exercise experimental day involved cycling for one hour at an intensity equivalent to 50% of maximum oxygen uptake and two hours of rest. The control condition comprised three hours of rest. Participants arrived at the laboratory fasted overnight; breakfast was standardised and an ad libitum pasta lunch was consumed on each experimental day. Participants kept a food diary to measure food intake and wore an Actiheart to measure energy expenditure for the remainder of the experimental days and over the subsequent 3 days. There was a condition effect for absolute energy intake (exercise vs. CONTROL: 3363 ± 668 kJ vs. 3035 ± 752 kJ; p = 0.033, d = 0.49) and relative energy intake (exercise vs. CONTROL: 2019 ± 746 kJ vs. 2710 ± 712 kJ; p <0.001, d = -1.00) at the ad libitum lunch. There were no significant differences in energy intake over the four days in active participants and there was a suppression of energy intake on the first day after the exercise experimental day compared with the same day of the control condition in inactive participants (mean difference = -1974 kJ; 95% CI -1048 to -2900 kJ, p = 0.002, d = -0.89). There was a group effect (p = 0.001, d = 1.63) for free-living energy expenditure, indicating that active participants expended more energy than inactive participants during this period. However, there were no compensatory changes in daily physical activity energy expenditure. These results support the use of low-intensity aerobic exercise as a method to induce a short-term negative energy balance in inactive women taking oral contraceptives.

Effects of a pragmatic lifestyle intervention for reducing body mass in obese adults with obstructive sleep apnoea: a randomised controlled trial.

This study investigated the effects of a pragmatic lifestyle intervention in obese adults with continuous positive airway pressure-treated obstructive sleep apnoea hypopnoea syndrome (OSAHS). Sixty patients were randomised 1 : 1 to either a 12-week lifestyle intervention or an advice-only control group. The intervention involved supervised exercise sessions, dietary advice, and the promotion of lifestyle behaviour change using cognitive-behavioural techniques. Outcomes were assessed at baseline (week 0), intervention end-point (week 13), and follow-up (week 26). The primary outcome was 13-week change in body mass. Secondary outcomes included anthropometry, blood-borne biomarkers, exercise capacity, and health-related quality of life. At end-point, the intervention group exhibited small reductions in body mass (-1.8 [-3.0, -0.5] kg; P = 0.007) and body fat percentage (-1 [-2, 0]%; P = 0.044) and moderate improvements in C-reactive protein (-1.3 [-2.4, -0.2] mg·L(-1); P = 0.028) and exercise capacity (95 [50, 139] m; P < 0.001). At follow-up, changes in body mass (-2.0 [-3.5, -0.5] kg; P = 0.010), body fat percentage (-1 [-2, 0]%; P = 0.033), and C-reactive protein (-1.3 [-2.5, -0.1] mg·L(-1); P = 0.037) were maintained and exercise capacity was further improved (132 [90, 175] m; P < 0.001). This trial is registered with ClinicalTrials.gov NCT01546792.

Multisite phosphorylation of the Sum1 transcriptional repressor by S-phase kinases controls exit from meiotic prophase in yeast.

Activation of the meiotic transcription factor Ndt80 is a key regulatory transition in the life cycle of Saccharomyces cerevisiae because it triggers exit from pachytene and entry into meiosis. The NDT80 promoter is held inactive by a complex containing the DNA-binding protein Sum1 and the histone deacetylase Hst1. Meiosis-specific phosphorylation of Sum1 by the protein kinases Cdk1, Ime2, and Cdc7 is required for NDT80 expression. Here, we show that the S-phase-promoting cyclin Clb5 activates Cdk1 to phosphorylate most, and perhaps all, of the 11 minimal cyclin-dependent kinase (CDK) phospho-consensus sites (S/T-P) in Sum1. Nine of these sites can individually promote modest levels of meiosis, yet these sites function in a quasiadditive manner to promote substantial levels of meiosis. Two Cdk1 sites and an Ime2 site individually promote high levels of meiosis, likely by preparing Sum1 for phosphorylation by Cdc7. Chromatin immunoprecipitation reveals that the phosphorylation sites are required for removal of Sum1 from the NDT80 promoter. We also find that Sum1, but not its partner protein Hst1, is required to repress NDT80 transcription. Thus, while the phosphorylation of Sum1 may lead to dissociation from DNA by influencing Hst1, it is the presence of Sum1 on DNA that determines whether NDT80 will be expressed.