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2.
J Behav Addict ; 12(4): 855-861, 2023 Dec 22.
Article in English | MEDLINE | ID: mdl-37934288

ABSTRACT

Background: The eleventh revision of the International Classification of Diseases (ICD-11) defines the three key diagnostic criteria for gaming disorder (GD). These are loss of control over gaming, gaming as a priority over daily activities, and impaired functioning due to gaming. While this definition has implications for the prevention and treatment of GD, there is significant heterogeneity in the symptoms and etiology of GD among individuals, which results in different treatment needs. Cognitive control, emotional regulation, and reward sensitivity are three critical dimensions in the etiology model for GD. Aspects such as gender, comorbidity, motivation for gaming, stage or severity of GD, and risk factors all contribute to the heterogeneity of etiology among individuals with the disorder. Method: On the basis of clinical symptoms and comorbidity characteristics among approximately 400 patients with gaming disorder, the present paper proposes a clinical typology of patients with GD based on the authors' clinical experience in treating individuals with GD. Results: The findings indicated three common types of patients with GD: (i) impulsive male patients with attention deficit hyperactivity disorder (ADHD), (ii) dysphoria patients with dysfunctional coping skills, and (iii) isolated patients with social anxiety. The paper also discusses the presentation and treatment priority for these patients. Conclusion: Personalized treatments for patients with GD should be developed to fit their individual needs. Future studies should examine the heterogeneity of GD and confirm these types, as well as obtain evidence-based information that can help in the development of personalized treatment. Treatment resources should be developed, and professionals should be trained to provide integrated individualized treatment.


Subject(s)
Behavior, Addictive , Disruptive, Impulse Control, and Conduct Disorders , Video Games , Humans , Male , Behavior, Addictive/diagnosis , Behavior, Addictive/therapy , Behavior, Addictive/psychology , Video Games/psychology , International Classification of Diseases , Impulsive Behavior
3.
ACS Omega ; 8(26): 23925-23935, 2023 Jul 04.
Article in English | MEDLINE | ID: mdl-37426216

ABSTRACT

We have developed an innovative system, AI QM Docking Net (AQDnet), which utilizes the three-dimensional structure of protein-ligand complexes to predict binding affinity. This system is novel in two respects: first, it significantly expands the training dataset by generating thousands of diverse ligand configurations for each protein-ligand complex and subsequently determining the binding energy of each configuration through quantum computation. Second, we have devised a method that incorporates the atom-centered symmetry function (ACSF), highly effective in describing molecular energies, for the prediction of protein-ligand interactions. These advancements have enabled us to effectively train a neural network to learn the protein-ligand quantum energy landscape (P-L QEL). Consequently, we have achieved a 92.6% top 1 success rate in the CASF-2016 docking power, placing first among all models assessed in the CASF-2016, thus demonstrating the exceptional docking performance of our model.

4.
Article in English | MEDLINE | ID: mdl-36901680

ABSTRACT

Internet addiction (IA) is defined as the condition of being addicted to all sorts of activities on the Internet. Individuals with neurodevelopmental disorders, including autism spectrum disorder (ASD), may be susceptible to IA. Early detection and intervention for probable IA are important to prevent severe IA. In this study, we investigated the clinical usefulness of a short version of the Internet Addiction Test (s-IAT) for the screening of IA among autistic adolescents. The subjects were 104 adolescents with a confirmed diagnosis of ASD. They were requested to answer 20 questions from the original Internet Addiction Test (IAT). In the data analysis process, we comparatively calculated the sum of scores to the 12 questions of s-IAT. In total, 14 of the 104 subjects were diagnosed as having IA based on the face-to-face clinical interview that was regarded as the gold standard. Statistical analysis suggested that the optimal cut-off for s-IAT was at 35. When we applied the cut-off of 70 on the IAT, only 2 of 14 subjects (14.3%) with IA were screened positive, whereas 10 (71.4%) of them were screened by using the cut-off point of 35 on s-IAT. The s-IAT might be useful for the screening of IA in adolescents with ASD.


Subject(s)
Autism Spectrum Disorder , Autistic Disorder , Behavior, Addictive , Humans , Adolescent , Internet Addiction Disorder , Behavior, Addictive/diagnosis , Cell Movement , Internet
5.
Front Psychiatry ; 13: 995665, 2022.
Article in English | MEDLINE | ID: mdl-36339875

ABSTRACT

Background: Digital gaming is the most common leisure activity among children and adolescents in Japan, especially in males. Playing online gaming has become more common among school-age children over the years. As a result, excessive online gaming in younger children has become a significant social problem in Japan. Previous studies have demonstrated that excessive online gaming could cause various mental health issues in children and adolescents. At medical institutions having child and adolescent psychiatry services, there is an increasing number of children and adolescents with various problems related to excessive gaming. The aim of this study was to investigate the current practice of gaming disorder (GD) in clinical settings in Japan. Methods: The subjects of this study were all of 414 child and adolescent psychiatrists certified by the Japanese Society for Child and Adolescent Psychiatry (JSCAP). The study questionnaire was mailed to all subjects from the official secretariat of JSCAP. Study subjects were requested to answer the questionnaire anonymously. The survey contained three types of responses: open responses; single and multiple-choice responses; and, responses on a five-point Likert scale. The questionnaire consisted of 14 questions regarding GD. Results: We received 159 responses. The most common reason for a visit to child and adolescent psychiatry service which results in a subsequent diagnosis of GD was school refusal/absenteeism followed by disruption of sleep-awake rhythm. The most common specialized treatment for GD currently offered at child and adolescent psychiatry service is individual psychotherapy. The two most frequently experienced difficulties in the treatment of GD were low motivation to achieve recovery and a large variety of combined problems other than excessive gaming itself. With regard to the three most common psychiatric comorbidities of GD, they were autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and depression. Discussion: The results of our survey revealed that although GD is a behavioral addiction, many children and adolescents with GD first visit child and adolescent psychiatry clinics rather than specialized clinics for addiction which are usually designed and staffed for adult patients. Because it is known that GD is more prevalent among young males, including junior high and high school students, GD has become one of the most important clinical issues in child and adolescent psychiatry today. The important roles of child and adolescent psychiatrists in the treatment of GD has been increasing.

7.
Curr Psychol ; : 1-19, 2022 Jul 29.
Article in English | MEDLINE | ID: mdl-35919757

ABSTRACT

The global pandemic of COVID-19 has forced people to restrict their outings. In Japan, self-restraint behavior (SRB) has been requested by the government, and some of those decreasing their outings may shift to pathological social withdrawal; hikikomori. The purpose of this study was to examine the risk factors of hikikomori conducting an online prospective survey. An online survey was conducted in June 2020 and December 2020; (1) SRB-related indicators (degree of SRB, motivation for SRB, stigma and self-stigma toward COVID-19, anxiety and depressive feelings toward COVID-19) and (2) general mental health (hikikomori tendency, depressive symptoms, modern type depression (MTD) tendency, internet addiction) were collected. A cross-lagged effects model was performed to examine the association between these variables. Lack of emotional support and lack of socialization in June 2020 increased isolation in December 2020. Besides, MTD and hikikomori interacted with each other. Interestingly, although hikikomori tendency increased depressive tendencies, SRB itself did not have a significant path on any mental health-related variables. Poor interpersonal relationships, rather than SRB per se, are suggested to be a risk factor for increased isolation among office workers in the COVID-19 pandemic. Appropriate early interventions such as interpersonal or emotional support may prevent the transition to pathological hikikomori. The association between MTD and hikikomori seems to reveal the interesting possibility that MTD is a gateway to increased risk of hikikomori, and that hikikomori is a gateway to MTD as well. Future research is required to elucidate the relationship between hikikomori and MTD.

8.
PLoS One ; 17(8): e0272803, 2022.
Article in English | MEDLINE | ID: mdl-35939449

ABSTRACT

BACKGROUND: We aimed to explore the overall network structure of problematic smartphone use symptoms assessed by smartphone addiction scale-short version (SAS-SV) and to identify which items could play important roles in the network. METHODS: 487 college and university students filled out the study questionnaire, including SAS-SV. We constructed a regularized partial correlation network among the 10 items of SAS-SV. We calculated three indices of node centrality: strength, closeness, and betweenness, to quantify the importance of each SAS-SV item. RESULTS: We identified 34 edges in the estimated network. In the given network, one item pertaining to withdrawal symptom hadthe highest strength and high closeness centrality. Additionally, one item related to preoccupation was also found to have high centrality indices. CONCLUSION: Our results indicating the central role of one withdrawal symptom and one preoccupation symptom in the symptom network of problematic smartphone use in young adults were in line with a previous study targeting school-age children. Longitudinal study designs are required to elicit the role of these central items on the formation and maintenance of this behavioral problem.


Subject(s)
Behavior, Addictive , Substance Withdrawal Syndrome , Behavior, Addictive/diagnosis , Behavior, Addictive/epidemiology , Child , Humans , Japan , Longitudinal Studies , Psychometrics , Smartphone , Young Adult
9.
Front Psychiatry ; 13: 1029653, 2022.
Article in English | MEDLINE | ID: mdl-36699498

ABSTRACT

Backgrounds: Hikikomori, pathological social withdrawal, is becoming a crucial mental health issue in Japan and worldwide. We have developed a 3-day family intervention program for hikikomori sufferers based on Mental Health First Aid (MHFA) and Community Reinforcement and Family Training (CRAFT). This study aims to confirm the effectiveness of the 3-day program by a randomized controlled trial. Methods: This study was registered on the UMIN Clinical Trials Registry (UMIN000037289). Fifteen parents were assigned to the treat as usual (TAU) group (TAU only; Age Mean, 65.6; SD, 7.8), and 14 to the Program group (program + TAU; Age Mean, 67.9; SD, 8.6). This study was discontinued due to the COVID-19 pandemic; the recruitment rate was 36.3% of our target sample size of 80. Results: Perceived skills improved temporally and stigma temporally worsened in the TAU group. Confidence decreased and attitude showed no change in both groups. Aggressive behaviors of hikikomori sufferers were significantly worsened in the Program group; however, no serious domestic violence was reported. In the TAU group, Avoidance and irregular life patterns were improved. Activity levels were worsened in both groups. Two participants (16.7%) in the Program group and one participant (7.7%) in the TAU group reported actual behavioral changes (e.g., utilizing support). Conclusion: We could not draw general conclusions on the effectiveness of the program due to the study discontinuation. Nevertheless, this study indicates the necessity for revision of the program to improve family members' confidence in engaging with hikikomori sufferers, with safer approaching by families.

11.
Soa Chongsonyon Chongsin Uihak ; 32(1): 35-40, 2021 Jan 01.
Article in English | MEDLINE | ID: mdl-33424240

ABSTRACT

OBJECTIVES: Among the many intervention programs for children with autism spectrum disorder (ASD), the Early Start Denver Model (ESDM) is one of the few approaches that has succeeded in demonstrating clinical efficacy in randomized control trials. Here, we inves-tigate the clinical efficacy of ESDM intervention in young children with ASD in a community setting within Japan. METHODS: All subjects were children with ASD who received ESDM intervention during the study period. Each ESDM session lasted 75 min and occurred once per week for at least 12 weeks. The outcome measures consisted of the Kyoto Scale of Psychological Develop-ment (K-test), Aberrant Behavior Checklist-Japanese version (ABC-J), and the Clinical Global Impression-Severity scale (CGI-S). RESULTS: Twenty-seven subjects (29.4±6.4 months old) received ESDM intervention that lasted for 8.0±2.6 months on average. The score on Language and Social developmental quotient on the K-test increased significantly after the intervention. The total scores on the ABC-J and CGI-S significantly decreased after completion of the ESDM intervention. CONCLUSION: Our results suggest that ESDM intervention could reduce the severity of distinct clinical features of ASD, such as impair-ments in social interaction and communication assessed by the K-test, and maladaptive behavior rated by the ABC-J and CGI-S. We be-lieve that the ESDM adapted to each institution might become one of the standard options for children with ASD in Japan.

12.
Sci Rep ; 10(1): 18550, 2020 10 29.
Article in English | MEDLINE | ID: mdl-33122676

ABSTRACT

Type II DNA topoisomerases (topo II) flip the spatial positions of two DNA duplexes, called G- and T- segments, by a cleavage-passage-resealing mechanism. In living cells, these DNA segments can be derived from distant sites on the same chromosome. Due to lack of proper methodology, however, no direct evidence has been described so far. The beta isoform of topo II (topo IIß) is essential for transcriptional regulation of genes expressed in the final stage of neuronal differentiation. Here we devise a genome-wide mapping technique (eTIP-seq) for topo IIß target sites that can measure the genomic distance between G- and T-segments. It revealed that the enzyme operates in two distinctive modes, termed proximal strand passage (PSP) and distal strand passage (DSP). PSP sites are concentrated around transcription start sites, whereas DSP sites are heavily clustered in small number of hotspots. While PSP represent the conventional topo II targets that remove local torsional stresses, DSP sites have not been described previously. Most remarkably, DSP is driven by the pairing between homologous sequences or repeats located in a large distance. A model-building approach suggested that topo IIß acts on crossovers to unknot the intertwined DSP sites, leading to chromatin decondensation.


Subject(s)
Chromatin/metabolism , DNA Topoisomerases, Type II/metabolism , DNA/metabolism , Animals , Cell Differentiation/physiology , DNA-Binding Proteins/metabolism , Neurons/metabolism , Protein Isoforms/metabolism , Rats , Rats, Wistar , Transcription Initiation Site/physiology
13.
Psychiatry Clin Neurosci ; 74(12): 652-658, 2020 Dec.
Article in English | MEDLINE | ID: mdl-32940406

ABSTRACT

AIM: Hikikomori, a form of pathological social withdrawal, has been suggested to have comorbidity with autism spectrum disorder (ASD). This study aimed to clarify how characteristics of hikikomori are associated with ASD, including undiagnosed autism spectrum conditions (ASC), in clinical settings. METHODS: A total of 416 clinical patients were recruited through the Mood Disorder/Hikikomori Clinic at Kyushu University Hospital. A total of 103 hikikomori cases and 221 clinical controls without hikikomori conditions were extracted using a semi-structured interview, and completed a series of self-rated scales, including the Japanese version of the Autism-Spectrum Quotient (AQ-J). RESULTS: Compared to non-hikikomori controls, hikikomori cases were more likely to have higher autistic tendency based on the AQ-J. The cases showed more severe subjective depressive symptoms based on the self-rated Beck Depression Inventory II, whereas no significant difference was found on interview-based severity evaluation using the Hamilton Depression Rating Scale. Comparison within hikikomori cases based on the AQ-J cut-off score revealed that hikikomori cases with high ASC were significantly more likely to have higher traits of modern-type depression, smaller social networks, and less social support. CONCLUSION: The present data suggest that hikikomori sufferers are more likely to have autistic tendency, and that hikikomori sufferers with high ASC may have much more difficulty in social communication and social interaction. In addition, those with high ASC may also have lower self-esteem and higher complaint tendencies as aspects of modern-type depression traits, which may relate to the occurrence of hikikomori. Thus, evaluating autistic tendencies is important for appropriate interventions in hikikomori. Further investigations should be conducted to validate our pilot findings using structured diagnostic systems of ASD.


Subject(s)
Autism Spectrum Disorder/physiopathology , Depressive Disorder/physiopathology , Social Interaction , Social Isolation , Social Networking , Social Support , Adult , Autism Spectrum Disorder/diagnosis , Autism Spectrum Disorder/epidemiology , Case-Control Studies , Comorbidity , Depressive Disorder/diagnosis , Depressive Disorder/epidemiology , Diagnostic Self Evaluation , Female , Humans , Interview, Psychological , Male , Pilot Projects , Psychiatric Status Rating Scales , Self Concept , Young Adult
14.
Curr Opin Psychiatry ; 33(3): 264-270, 2020 05.
Article in English | MEDLINE | ID: mdl-32101902

ABSTRACT

PURPOSE OF REVIEW: Internet society has made our daily life more convenient, while its negative consequences especially internet, smartphone, and gaming addiction are emerging. At the same time, the phenomenon of pathological social withdrawal called 'hikikomori' has been increasingly highlighted as a problematic behavior in Japan. Now hikikomori is becoming a global mental health issue. The interaction between internet society, internet addiction, and hikikomori has not been well clarified. RECENT FINDINGS: A case vignette survey among psychiatrists suggested that hikikomori cases could be comorbid with internet addiction. In reality, hikikomori cases with internet addiction have been reported internationally. A recent survey among college/university students in Japan has indicated positive interactions between internet addiction, smartphone addiction, gaming internet disorder, and hikikomori-tendencies. SUMMARY: The cause of hikikomori has not been well understood, and the emergence of internet may be one of the important contributing factors for the occurrence of hikikomori. Whether pathological social withdrawal creates internet addiction, or internet overuse creates hikikomori remains unclear. Both possibilities exist, and we herein propose the conceptual model of these hypothetical interactions. Clarifying the mechanisms of both conditions will help to solve these crucial issues for contemporary urban societies.


Subject(s)
Internet Addiction Disorder/psychology , Mental Disorders/psychology , Social Isolation/psychology , Humans , Internet , Japan , Students
15.
Heliyon ; 6(1): e03011, 2020 Jan.
Article in English | MEDLINE | ID: mdl-31938741

ABSTRACT

BACKGROUNDS: Hikikomori, a severe form of social withdrawal, is increasingly a serious mental health issue worldwide. Hikikomori is comorbid with various psychiatric conditions including depression, social anxiety and suicidal behaviors. Family support is encouraged as a vital first step, however evidence-based programs have yet to be established. Mental Health First Aid (MHFA) is one of the most well-validated educational programs encouraging lay people such as family members, to support close persons suffering from various psychiatric conditions such as depression, anxiety and suicidal behaviors. METHODS: We newly developed an educational program for family members of hikikomori sufferers mainly based on MHFA and 'Community Reinforcement and Family Training (CRAFT)' with role-play and homework. As a single-arm trial, 21 parents (7 fathers and 14 mothers) living with hikikomori sufferers participated in our program with five once-a-week sessions (2 h per session) and six monthly follow-ups, and its effectiveness was evaluated using various self-rated questionnaires. RESULTS: Perceived skills toward a depressed hikikomori case vignette, stigma held by participants, and subscales of two problematic and one adaptive behaviors of hikikomori sufferers were improved throughout the sessions and follow-ups. In addition, positive behavioral changes of hikikomori sufferers such as improved social participation were reported by participants. LIMITATIONS: Single-arm design and evaluation using self-rated questionnaires are the main limitations of the present study. CONCLUSIONS: Our newly developed program has positive effects on family members in their contact and support of hikikomori sufferers. Future trials with control groups are required to validate the effectiveness of this program.

16.
World J Clin Cases ; 7(12): 1483-1491, 2019 Jun 26.
Article in English | MEDLINE | ID: mdl-31363477

ABSTRACT

BACKGROUND: Familial idiopathic basal ganglia calcification (FIBGC) is a rare autosomal dominant disorder that causes bilateral calcification of the basal ganglia and/or cerebellar dentate nucleus, among other locations. CASE SUMMARY: The aim of this study is to report 10 cases of FIBGC observed in a single family. Seven patients showed calcification on their computed tomography scan, and all of these patients carried the SLC20A2 mutation. However, individuals without the mutation did not show calcification. Three patients among the 7 with calcification were symptomatic, while the remaining 4 patients were asymptomatic. Additionally, we longitudinally observed 10 subjects for ten years. In this paper, we mainly focus on the clinical course and neuroradiological findings in the proband and her son. CONCLUSION: The accumulation of more case reports and further studies related to the manifestation of FIBGC are needed.

17.
Psychiatry Investig ; 16(7): 554-557, 2019 Jul.
Article in English | MEDLINE | ID: mdl-31352738

ABSTRACT

Little is known about the treatment of gender dysphoria among children and adolescents in Japan. This preliminary survey aims to improve understanding of current clinical practice for treatment of children with gender dysphoria. Subjects were 315 certified child and adolescent psychiatrists in Japan. The questionnaire asked about clinical experiences concerning gender dysphoria and gender identityrelated concerns. A total of 128 psychiatrists responded to the questionnaire. Mean length of clinical experience was 24.2±10.0 years in total and 16.9±11.5 years as child and adolescent psychiatry specialists. Among the respondents, 74 (57.8%) had seen children and adolescents with DSM-5 gender dysphoria, and 87 (67.7%) had examined cases with gender identity-related concerns. The mean number of experienced cases with gender dysphoria was 1.80±2.3 per respondent. We found that even among certified child and adolescent psychiatrists in Japan, experience with treatment of children with gender dysphoria was limited.

18.
Front Psychiatry ; 10: 455, 2019.
Article in English | MEDLINE | ID: mdl-31354537

ABSTRACT

Background: As the number of internet users increases, problems related to internet overuse are becoming more and more serious. Adolescents and youth may be particularly attracted to and preoccupied with various online activities. In this study, we investigated the relationship of internet addiction, smartphone addiction, and the risk of hikikomori, severe social withdrawal, in Japanese young adult. Methods: The subjects were 478 college/university students in Japan. They were requested to complete the study questionnaire, which consisted of questions about demographics, internet use, the Internet Addiction Test (IAT), the Smartphone Addiction Scale (SAS)-Short Version (SV), the 25-item Hikikomori Questionnaire (HQ-25), etc. We investigated the difference and correlation of the results between two groups based on the purpose of internet use or the total score of each self-rating scale, such as screened positive or negative for the risk of internet addiction, smartphone addiction, or hikikomori. Results: There was a trend that males favored gaming in their internet use while females used the internet mainly for social networking via smartphone, and the mean SAS-SV score was higher in females. Two-group comparisons between gamers and social media users, according to the main purpose of internet use, showed that gamers used the internet longer and had significantly higher mean IAT and HQ-25 scores. Regarding hikikomori trait, the subjects at high risk for hikikomori on HQ-25 had longer internet usage time and higher scores on both IAT and SAS-SV. Correlation analyses revealed that HQ-25 and IAT scores had a relatively strong relationship, although HQ-25 and SAS-SV had a moderately weak one. Discussion: Internet technology has changed our daily lives dramatically and altered the way we communicate as well. As social media applications are becoming more popular, users are connected more tightly to the internet and their time spent with others in the real world continues to decrease. Males often isolate themselves from the social community in order to engage in online gaming while females use the internet as to not be excluded from their communications online. Mental health providers should be aware of the seriousness of internet addictions and hikikomori.

19.
Psychiatry Clin Neurosci ; 73(8): 448-457, 2019 Aug.
Article in English | MEDLINE | ID: mdl-30900331

ABSTRACT

AIM: Understanding premorbid personality is important, especially when considering treatment selection. Historically, the premorbid personality of patients with major depression in Japan was described as Shuchaku-kishitsu [similar to Typus melancholicus], as proposed by Shimoda in the 1930s. Since around 2000, there have been increased reports in Japan of young adults with depression who have had premorbid personality differing from the traditional type. In 2005, Tarumi termed this novel condition 'dysthymic-type depression,' and more recently the condition has been called Shin-gata/Gendai-gata Utsu-byo [modern-type depression (MTD)]. We recently developed a semi-structured diagnostic interview to evaluate MTD. Development of a tool that enables understanding of premorbid personality in a short time, especially at the early stage of treatment, is desirable. The object of this study was to develop a self-report scale to evaluate the traits of MTD, and to assess the scale's psychometric properties, diagnostic accuracy, and biological validity. METHODS: A sample of 340 participants from clinical and community settings completed measures. Psychometric properties were assessed with factor analysis. Diagnostic accuracy of the MTD traits was compared against a semi-structured interview. RESULTS: The questionnaire contained 22 items across three subscales, thus we termed it the 22-item Tarumi's Modern-Type Depression Trait Scale: Avoidance of Social Roles, Complaint, and Low Self-Esteem (TACS-22). Internal consistency, test-retest reliability, and convergent validity were all satisfactory. Among patients with major depression, the area under the curve was 0.757 (sensitivity of 63.1% and specificity of 82.9%) and the score was positively correlated with plasma tryptophan. CONCLUSION: The TACS-22 possessed adequate psychometric properties and diagnostic accuracy in an initial sample of Japanese adults. Additional research on its ability to support clinical assessment of MTD is warranted.


Subject(s)
Depression/diagnosis , Prodromal Symptoms , Psychiatric Status Rating Scales/statistics & numerical data , Self Concept , Social Behavior , Adolescent , Adult , Depression/blood , Female , Humans , Male , Middle Aged , Psychometrics , Self Report , Sensitivity and Specificity , Tryptophan/blood , Young Adult
20.
Glycobiology ; 29(7): 576-587, 2019 07 01.
Article in English | MEDLINE | ID: mdl-30913288

ABSTRACT

Fucosylation of the N-glycan core via the α1-6 linkage (core fucosylation) is detected in specific types of cancers and related diseases, and thereby serves for a relevant biomarker. The lectin from a mushroom Pholiota squarrosa (PhoSL) shows a clear specificity to core fucosylation, without recognizing those with other types of fucosylation, such as the H type via the α1-2 linkage or the Lewis type via the α1-3 or α1-4 linkage. Here we determined the crystal structure of the PhoSL trimer in complex with a disaccharide fucose(α1-6)N-acetylglucosamine (GlcNAc). In the three sugar-binding pockets of PhoSL, extensive hydrophobic and hydrogen-bonding contacts were formed with the fucose moiety. In contrast, the GlcNAc moiety showed only a few hydrophobic and hydrogen-bonding contacts. To elucidate the mechanism for the specificity, we performed molecular dynamics simulations on this disaccharide and a trisaccharide fucose(α1-6)[GlcNAc(ß1-4)]GlcNAc in complex with PhoSL. It was observed that the GlcNAc corresponding to the outer one of the N-glycan core entered the sugar-binding pocket with the N-acetyl group placed stably at the bottom, forming extensive hydrophobic and hydrogen-bonding interactions. In addition, these glycans adopted unstressed favorable conformations when bound to PhoSL. In contrast, H- and Lewis-types of fucosylated trisaccharides adopting favorable conformations caused inevitable steric hindrance with the steep edge of the binding pocket, when docked with PhoSL. Therefore, the specificity to core fucosylation of PhoSL was achieved by a combination of these preferential and exclusive mechanisms.


Subject(s)
Fucose/metabolism , Pholiota/metabolism , Polysaccharides/metabolism , Carbohydrate Conformation , Fucose/chemistry , Molecular Dynamics Simulation , Polysaccharides/chemistry
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