Protein semisynthesis underscores the role of a conserved lysine in activation and desensitization of acid-sensing ion channels.

Acid-sensing ion channels (ASICs) are trimeric ion channels that open a cation-conducting pore in response to proton binding. Excessive ASIC activation during prolonged acidosis in conditions such as inflammation and ischemia is linked to pain and stroke. A conserved lysine in the extracellular domain (Lys211 in mASIC1a) is suggested to play a key role in ASIC function. However, the precise contributions are difficult to dissect with conventional mutagenesis, as replacement of Lys211 with naturally occurring amino acids invariably changes multiple physico-chemical parameters. Here, we study the contribution of Lys211 to mASIC1a function using tandem protein trans-splicing (tPTS) to incorporate non-canonical lysine analogs. We conduct optimization efforts to improve splicing and functionally interrogate semisynthetic mASIC1a. In combination with molecular modeling, we show that Lys211 charge and side-chain length are crucial to activation and desensitization, thus emphasizing that tPTS can enable atomic-scale interrogations of membrane proteins in live cells.

Time-resolved cryo-EM (TR-EM) analysis of substrate polyubiquitination by the RING E3 anaphase-promoting complex/cyclosome (APC/C).

Substrate polyubiquitination drives a myriad of cellular processes, including the cell cycle, apoptosis and immune responses. Polyubiquitination is highly dynamic, and obtaining mechanistic insight has thus far required artificially trapped structures to stabilize specific steps along the enzymatic process. So far, how any ubiquitin ligase builds a proteasomal degradation signal, which is canonically regarded as four or more ubiquitins, remains unclear. Here we present time-resolved cryogenic electron microscopy studies of the 1.2 MDa E3 ubiquitin ligase, known as the anaphase-promoting complex/cyclosome (APC/C), and its E2 co-enzymes (UBE2C/UBCH10 and UBE2S) during substrate polyubiquitination. Using cryoDRGN (Deep Reconstructing Generative Networks), a neural network-based approach, we reconstruct the conformational changes undergone by the human APC/C during polyubiquitination, directly visualize an active E3-E2 pair modifying its substrate, and identify unexpected interactions between multiple ubiquitins with parts of the APC/C machinery, including its coactivator CDH1. Together, we demonstrate how modification of substrates with nascent ubiquitin chains helps to potentiate processive substrate polyubiquitination, allowing us to model how a ubiquitin ligase builds a proteasomal degradation signal.

The effect of the bgs13 mutation on the structure of the reporter protein beta-lactoglobulin: Influence on folding and aggregation in Pichia pastoris.

Pichia pastoris, a methylotrophic yeast used for recombinant protein expression, has the capability of performing many eukaryotic post-translational modifications, growing to high cell densities, and producing proteins in a cost-effective manner. However, P. pastoris's secretion properties are not always efficient, and its secretory pathway mechanisms have not been thoroughly elucidated. A previously identified mutant strain, bgs13, was found to efficiently secrete most recombinant proteins tested, raising the possibility that this bgs13 mutant is a universal super secreter. In this study, we used a reporter protein, ß-lactoglobulin (b-LG), to perform structural analysis of the protein secreted from wild type and mutant bgs13 strains to investigate the secretory mechanism. Primary, secondary, and tertiary structures of b-LG were examined using Edman sequencing, circular dichroism, tryptophan fluorescence, and temperature induced aggregation analysis. Our results demonstrate that the bgs13 produced more b-LG than the wt strain and that this protein was functionally folded similar to the wt. Surprisingly, we also found that the bgs13 b-LG was more resistant to aggregation, providing another example of the superior qualities of this strain for enhanced secreted protein production.

Inside-Out Design of Zinc-Binding Proteins with Non-Native Backbones.

The de novo design of functional proteins requires specification of tertiary structure and incorporation of molecular binding sites. Here, we develop an inside-out design strategy in the molecular modeling program Rosetta that begins with amino acid side chains from one or two α-helices making well-defined contacts with a ligand. A full-sized protein is then built around the ligand by adding additional helices that promote the formation of a protein core and allow additional contacts with the ligand. The protocol was tested by designing 12 zinc-binding proteins, each with 4-5 helices. Four of the designs were folded and bound to zinc with equilibrium dissociation constants varying between 95 nM and 1.1 µM. The design with the tightest affinity for zinc, N12, adopts a unique conformation in the folded state as assessed with nuclear magnetic resonance (NMR) and the design model closely matches (backbone root-mean-square deviation (RMSD) < 1 Å) an AlphaFold model of the sequence. Retrospective analysis with AlphaFold suggests that the sequences of many of the failed designs did not encode the desired tertiary packing.

Leveraging behavioral economics and implementation science to engage patients at risk for suicide in mental health treatment: a pilot study protocol.

BACKGROUND: Primary care is an ideal setting to connect individuals at risk for suicide to follow-up care; however, only half of the patients referred from the primary care attend an initial mental health visit. We aim to develop acceptable, feasible, low-cost, and effective new strategies to increase treatment initiation among at-risk individuals identified in primary care. METHODS: We will conduct a multi-phase, mixed-methods study. First, we will conduct a chart review study by using administrative data, including medical records, to identify characteristics of primary care patients at risk for suicide who do or do not attend an initial mental health visit following a referral. Second, we will conduct a mixed methods study by using direct observations and qualitative interviews with key stakeholders (N = 65) to understand barriers and facilitators to mental health service initiation among at-risk individuals. Stakeholders will include patients with suicidal ideation referred from primary care who do and do not attend a first mental health visit, primary care and behavioral health providers, and individuals involved in the referral process. We also will collect preliminary self-report and behavioral data regarding potential mechanisms of behavior change (i.e., self-regulation and social support) from patients. Third, we will leverage these findings, relevant frameworks, and the extant literature to conduct a multi-arm, non-randomized feasibility trial. During this trial, we will rapidly prototype and test strategies to support attendance at initial mental health visits. Strategies will be developed with subject matter experts (N = 10) and iteratively pilot tested (~5 patients per strategy) and refined. Research will be completed in the Penn Integrated Care Program (PIC), which includes fourteen primary care clinics in Philadelphia that provide infrastructure for electronic referrals, patient communication, and data access. DISCUSSION: We will leverage frameworks and methods from behavioral economics and implementation science to develop strategies to increase mental health treatment initiation among individuals at risk for suicide identified in primary care. This project will lead to an evaluation of these strategies in a fully powered randomized trial and contribute to improvements in access to and engagement in mental health services for individuals at risk for suicide. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05021224.

Insight into Viral Hijacking of CRL4 Ubiquitin Ligase through Structural Analysis of the pUL145-DDB1 Complex.

Viruses evolve mechanisms to exploit cellular pathways that increase viral fitness, e.g., enhance viral replication or evade the host cell immune response. The ubiquitin-proteosome system, a fundamental pathway-regulating protein fate in eukaryotes, is hijacked by all seven classes of viruses. Members of the Cullin-RING family of ubiquitin (Ub) ligases are frequently co-opted by divergent viruses because they can target a broad array of substrates by forming multisubunit assemblies comprised of a variety of adapters and substrate receptors. For example, the linker subunit DDB1 in the cullin 4-RING (CRL4)-DDB1 Ub ligase (CRL4DDB1) interacts with an H-box motif found in several unrelated viral proteins, including the V protein of simian virus 5 (SV5-V), the HBx protein of hepatitis B virus (HBV), and the recently identified pUL145 protein of human cytomegalovirus (HCMV). In HCMV-infected cells, pUL145 repurposes CRL4DDB1 to target STAT2, a protein vital to the antiviral immune response. However, the details of how these divergent viral sequences hijack DDB1 is not well understood. Here, we use a combination of binding assays, X-ray crystallography, alanine scanning, cell-based assays, and computational analysis to reveal that viral H-box motifs appear to bind to DDB1 with a higher affinity than the H-box motifs from host proteins DCAF1 and DDB2. This analysis reveals that viruses maintain native hot-spot residues in the H-box motif of host DCAFs and also acquire favorable interactions at neighboring residues within the H-box. Overall, these studies reveal how viruses evolve strategies to produce high-affinity binding and quality interactions with DDB1 to repurpose its Ub ligase machinery. IMPORTANCE Many different viruses modulate the protein machinery required for ubiquitination to enhance viral fitness. Specifically, several viruses hijack the cullin-RING ligase CRL4DDB1 to degrade host resistance factors. Human cytomegalovirus (HCMV) encodes pUL145 that redirects CRL4DDB1 to evade the immune system through the targeted degradation of the antiviral immune response protein STAT2. However, it is unclear why several viruses bind specific surfaces on ubiquitin ligases to repurpose their activity. We demonstrate that viruses have optimized H-box motifs that bind DDB1 with higher affinity than the H-box of native binders. For viral H-boxes, native interactions are maintained, but additional interactions that are absent in host cell H-boxes are formed, indicating that rewiring CRL4DDB1 creates a selective advantage for the virus. The DDB1-pUL145 peptide structure reveals that water-mediated interactions are critical to the higher affinity. Together, our data present an interesting example of how viral evolution can exploit a weakness in the ubiquitination machinery.

Coevolutionary Analysis Implicates Toll-Like Receptor 9 in Papillomavirus Restriction.

Upon infection, DNA viruses can be sensed by pattern recognition receptors (PRRs), leading to the activation of type I and III interferons to block infection. Therefore, viruses must inhibit these signaling pathways, avoid being detected, or both. Papillomavirus virions are trafficked from early endosomes to the Golgi apparatus and wait for the onset of mitosis to complete nuclear entry. This unique subcellular trafficking strategy avoids detection by cytoplasmic PRRs, a property that may contribute to the establishment of infection. However, as the capsid uncoats within acidic endosomal compartments, the viral DNA may be exposed to detection by Toll-like receptor 9 (TLR9). In this study, we characterized two new papillomaviruses from bats and used molecular archeology to demonstrate that their genomes altered their nucleotide compositions to avoid detection by TLR9, providing evidence that TLR9 acts as a PRR during papillomavirus infection. Furthermore, we showed that TLR9, like other components of the innate immune system, is under evolutionary selection in bats, providing the first direct evidence for coevolution between papillomaviruses and their hosts. Finally, we demonstrated that the cancer-associated human papillomaviruses show a reduction in CpG dinucleotides within a TLR9 recognition complex. IMPORTANCE Viruses must avoid detection by the innate immune system. In this study, we characterized two new papillomaviruses from bats and used molecular archeology to demonstrate that their genomes altered their nucleotide compositions to avoid detection by TLR9, providing evidence that TLR9 acts as a PRR during papillomavirus infection. Furthermore, we demonstrated that TLR9, like other components of the innate immune system, is under evolutionary selection in bats, providing the first direct evidence for coevolution between papillomaviruses and their hosts.

From Protein Design to the Energy Landscape of a Cold Unfolding Protein.

Understanding protein folding is crucial for protein sciences. The conformational spaces and energy landscapes of cold (unfolded) protein states, as well as the associated transitions, are hardly explored. Furthermore, it is not known how structure relates to the cooperativity of cold transitions, if cold and heat unfolded states are thermodynamically similar, and if cold states play important roles for protein function. We created the cold unfolding 4-helix bundle DCUB1 with a de novo designed bipartite hydrophilic/hydrophobic core featuring a hydrogen bond network which extends across the bundle in order to study the relative importance of hydrophobic versus hydrophilic protein-water interactions for cold unfolding. Structural and thermodynamic characterization resulted in the discovery of a complex energy landscape for cold transitions, while the heat unfolded state is a random coil. Below ∼0 °C, the core of DCUB1 disintegrates in a largely cooperative manner, while a near-native helical content is retained. The resulting cold core-unfolded state is compact and features extensive internal dynamics. Below -5 °C, two additional cold transitions are seen, that is, (i) the formation of a water-mediated, compact, and highly dynamic dimer, and (ii) the onset of cold helix unfolding decoupled from cold core unfolding. Our results suggest that cold unfolding is initiated by the intrusion of water into the hydrophilic core network and that cooperativity can be tuned by varying the number of core hydrogen bond networks. Protein design has proven to be invaluable to explore the energy landscapes of cold states and to robustly test related theories.

Functional conservation and divergence of the helix-turn-helix motif of E2 ubiquitin-conjugating enzymes.

Polyubiquitination by E2 and E3 enzymes is crucial to cell cycle control, epigenetic regulation, and development. The hallmark of the E2 family is the ubiquitin (Ub)-conjugating (UBC) domain that forms a dynamic thioester conjugate with ubiquitin (E2~Ub). Numerous studies have focused on E2 surfaces, such as the N-terminal and crossover helices, that directly interact with an E3 or the conjugated ubiquitin to stabilize the active, "closed" state of the E2~Ub. However, it remains unclear how other E2 surfaces regulate ubiquitin transfer. Here, we demonstrate the helix-turn-helix (HTH) motif of the UBC tunes the intrinsic polyubiquitination activity through distinct functions in different E2s. Interestingly, the E2HTH motif is repurposed in UBE2S and UBE2R2 to interact with the conjugated or acceptor ubiquitin, respectively, modulating ubiquitin transfer. Furthermore, we propose that Anaphase-Promoting Complex/Cyclosome binding to the UBE2SHTH reduces the conformational space of the flexible E2~Ub, demonstrating an atypical E3-dependent activation mechanism. Altogether, we postulate the E2HTH motif evolved to provide new functionalities that can be harnessed by E3s and permits additional regulation to facilitate specific E2-E3-mediated polyubiquitination.

Identification of disease-linked hyperactivating mutations in UBE3A through large-scale functional variant analysis.

The mechanisms that underlie the extensive phenotypic diversity in genetic disorders are poorly understood. Here, we develop a large-scale assay to characterize the functional valence (gain or loss-of-function) of missense variants identified in UBE3A, the gene whose loss-of-function causes the neurodevelopmental disorder Angelman syndrome. We identify numerous gain-of-function variants including a hyperactivating Q588E mutation that strikingly increases UBE3A activity above wild-type UBE3A levels. Mice carrying the Q588E mutation exhibit aberrant early-life motor and communication deficits, and individuals possessing hyperactivating UBE3A variants exhibit affected phenotypes that are distinguishable from Angelman syndrome. Additional structure-function analysis reveals that Q588 forms a regulatory site in UBE3A that is conserved among HECT domain ubiquitin ligases and perturbed in various neurodevelopmental disorders. Together, our study indicates that excessive UBE3A activity increases the risk for neurodevelopmental pathology and suggests that functional variant analysis can help delineate mechanistic subtypes in monogenic disorders.

Designed, highly expressing, thermostable dengue virus 2 envelope protein dimers elicit quaternary epitope antibodies.

Dengue virus (DENV) is a worldwide health burden, and a safe vaccine is needed. Neutralizing antibodies bind to quaternary epitopes on DENV envelope (E) protein homodimers. However, recombinantly expressed soluble E proteins are monomers under vaccination conditions and do not present these quaternary epitopes, partly explaining their limited success as vaccine antigens. Using molecular modeling, we found DENV2 E protein mutations that induce dimerization at low concentrations (<100 pM) and enhance production yield by more than 50-fold. Cross-dimer epitope antibodies bind to the stabilized dimers, and a crystal structure resembles the wild-type (WT) E protein bound to a dimer epitope antibody. Mice immunized with the stabilized dimers developed antibodies that bind to E dimers and not monomers and elicited higher levels of DENV2-neutralizing antibodies compared to mice immunized with WT E antigen. Our findings demonstrate the feasibility of using structure-based design to produce subunit vaccines for dengue and other flaviviruses.

Effect of Goal-Setting Approaches Within a Gamification Intervention to Increase Physical Activity Among Economically Disadvantaged Adults at Elevated Risk for Major Adverse Cardiovascular Events: The ENGAGE Randomized Clinical Trial.

Importance: Health promotion efforts commonly communicate goals for healthy behavior, but the best way to design goal setting among high-risk patients has not been well examined. Objective: To test the effectiveness of different ways to set and implement goals within a behaviorally designed gamification intervention to increase physical activity. Design, Setting, and Participants: Evaluation of the Novel Use of Gamification With Alternative Goal-setting Experiences was conducted from January 15, 2019, to June 1, 2020. The 24-week randomized clinical trial included a remotely monitored 8-week introductory intervention period, 8-week maintenance intervention period, and 8-week follow-up period. A total of 500 adults from lower-income neighborhoods in and around Philadelphia, Pennsylvania, who had either an atherosclerotic cardiovascular disease (ASCVD) condition or a 10-year ASCVD risk score greater than or equal to 7.5% were enrolled. Participants were paid for enrolling in and completing the trial. Interventions: All participants used a wearable device to track daily steps, established a baseline level, and were then randomly assigned to an attention control or 1 of 4 gamification interventions that varied only on how daily step goals were set (self-chosen or assigned) and implemented (immediately or gradually). Main Outcome Measures: The primary outcome was change in mean daily steps from baseline to the 8-week maintenance intervention period. Other outcomes included changes in minutes of moderate to vigorous physical activity. All randomly assigned participants were included in the intention-to-treat analysis. Results: Of the 500 participants, 331 individuals (66.2%) were Black, 114 were White (22.8%), and 348 were women (69.6%). Mean (SD) age was 58.5 (10.8) years and body mass index was 33.2 (7.8). A total of 215 participants (43.0%) had an ASCVD condition. Compared with the control arm, participants with self-chosen and immediate goals had significant increases in the number of daily steps during the maintenance intervention period (1384; 95% CI, 805-1963; P < .001) that were sustained during the 8-week follow-up (1391; 95% CI, 785-1998; P < .001). This group also had significant increases in daily minutes of moderate to vigorous physical activity during the maintenance intervention (4.1; 95% CI, 1.8-6.4; P < .001) that were sustained during follow-up (3.5; 95% CI, 1.1-5.8; P = .004). No other gamification arms had consistent increases in physical activity compared with the control arm. No major adverse events were reported. Conclusions and Relevance: In this trial among economically disadvantaged adults at elevated risk for major adverse cardiovascular events, a gamification intervention led to increases in physical activity that were sustained during 8 weeks of follow-up when goals were self-chosen and implemented immediately. Trial Registration: ClinicalTrials.gov Identifier: NCT03749473.

Mechanically transduced immunosorbent assay to measure protein-protein interactions.

Measuring protein-protein interaction (PPI) affinities is fundamental to biochemistry. Yet, conventional methods rely upon the law of mass action and cannot measure many PPIs due to a scarcity of reagents and limitations in the measurable affinity ranges. Here, we present a novel technique that leverages the fundamental concept of friction to produce a mechanical signal that correlates to binding potential. The mechanically transduced immunosorbent (METRIS) assay utilizes rolling magnetic probes to measure PPI interaction affinities. METRIS measures the translational displacement of protein-coated particles on a protein-functionalized substrate. The translational displacement scales with the effective friction induced by a PPI, thus producing a mechanical signal when a binding event occurs. The METRIS assay uses as little as 20 pmols of reagents to measure a wide range of affinities while exhibiting a high resolution and sensitivity. We use METRIS to measure several PPIs that were previously inaccessible using traditional methods, providing new insights into epigenetic recognition.

Effect of Behaviorally Designed Gamification With Social Incentives on Lifestyle Modification Among Adults With Uncontrolled Diabetes: A Randomized Clinical Trial.

Importance: Gamification is increasingly being used to promote healthy behaviors. However, it has not been well tested among patients with chronic conditions and over longer durations. Objective: To test the effectiveness of behaviorally designed gamification interventions to enhance support, collaboration, or competition to promote physical activity and weight loss among adults with uncontrolled type 2 diabetes. Design, Setting, and Participants: A 4-arm randomized clinical trial with a 1-year intervention was conducted from January 23, 2017, to January 27, 2020, with remotely monitored intervention. Analyses were conducted between February 10 and October 6, 2020. Participants included 361 adults with type 2 diabetes with hemoglobin A1c levels greater than or equal to 8% and body mass index greater than or equal to 25. Interventions: All participants received a wearable device, smart weight scale, and laboratory testing. Participants in the control group received feedback from their devices but no other interventions. Participants in the gamification arms conducted goal setting and were entered into a 1-year game designed using insights from behavioral economics with points and levels for achieving step goals and weight loss targets. The game varied by trial arm to promote either support, collaboration, or competition. Main Outcomes and Measures: Co-primary outcomes included daily step count, weight, and hemoglobin A1c level. Secondary outcome was low-density lipoprotein cholesterol level. Intention-to-treat analysis was used. Results: Participants had a mean (SD) age of 52.5 (10.1) years; hemoglobin A1c level, 9.6% (1.6%); daily steps, 4632 (2523); weight, 107.4 kg (20.8 kg); and body mass index, 37.1 (6.6). Of the 361 participants, 202 (56.0%) were women, 143 (39.6%) were White, and 185 (51.2%) were Black; with 87 (24.1%) randomized to control; 92 (25.4%) randomized to gamification with support and intervention; 95 (26.3%) randomized to gamification with collaboration; and 87 (24.1%) randomized to gamification with competition. Compared with the control group over 1 year, there was a significant increase in mean daily steps from baseline among participants receiving gamification with support (adjusted difference relative to control group, 503 steps; 95% CI, 103 to 903 steps; P = .01) and competition (606 steps; 95% CI, 201 to 1011 steps; P = .003) but not collaboration (280 steps; 95% CI, -115 to 674 steps; P = .16). All trial arms had significant reductions in weight and hemoglobin A1c levels from baseline, but there were no significant differences between any of the intervention arms and the control arm. There was only 1 adverse event reported that may have been related to the trial (arthritic knee pain). Conclusions and Relevance: Among adults with uncontrolled type 2 diabetes, a behaviorally designed gamification intervention in this randomized clinical trial significantly increased physical activity over a 1-year period when designed to enhance either support or competition but not collaboration. No differences between intervention and control groups were found for other outcomes. Trial Registration: ClinicalTrials.gov Identifier: NCT02961192.

Linkage-specific ubiquitin chain formation depends on a lysine hydrocarbon ruler.

Virtually all aspects of cell biology are regulated by a ubiquitin code where distinct ubiquitin chain architectures guide the binding events and itineraries of modified substrates. Various combinations of E2 and E3 enzymes accomplish chain formation by forging isopeptide bonds between the C terminus of their transiently linked donor ubiquitin and a specific nucleophilic amino acid on the acceptor ubiquitin, yet it is unknown whether the fundamental feature of most acceptors-the lysine side chain-affects catalysis. Here, use of synthetic ubiquitins with non-natural acceptor site replacements reveals that the aliphatic side chain specifying reactive amine geometry is a determinant of the ubiquitin code, through unanticipated and complex reliance of many distinct ubiquitin-carrying enzymes on a canonical acceptor lysine.

In silico APC/C substrate discovery reveals cell cycle-dependent degradation of UHRF1 and other chromatin regulators.

The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase and critical regulator of cell cycle progression. Despite its vital role, it has remained challenging to globally map APC/C substrates. By combining orthogonal features of known substrates, we predicted APC/C substrates in silico. This analysis identified many known substrates and suggested numerous candidates. Unexpectedly, chromatin regulatory proteins are enriched among putative substrates, and we show experimentally that several chromatin proteins bind APC/C, oscillate during the cell cycle, and are degraded following APC/C activation, consistent with being direct APC/C substrates. Additional analysis revealed detailed mechanisms of ubiquitylation for UHRF1, a key chromatin regulator involved in histone ubiquitylation and DNA methylation maintenance. Disrupting UHRF1 degradation at mitotic exit accelerates G1-phase cell cycle progression and perturbs global DNA methylation patterning in the genome. We conclude that APC/C coordinates crosstalk between cell cycle and chromatin regulatory proteins. This has potential consequences in normal cell physiology, where the chromatin environment changes depending on proliferative state, as well as in disease.

Designing Nudges for Success in Health Care.

Nudges are subtle changes to the design of the environment or the framing of information that can influence our behaviors. There is significant potential to use nudges in health care to improve patient outcomes and transform health care delivery. However, these interventions must be tested and implemented using a systematic approach. In this article, we describe several ways to design nudges for success by focusing on optimizing and fitting them into the clinical workflow, engaging the right stakeholders, and rapid experimentation.

Association between behavioral phenotypes and response to a physical activity intervention using gamification and social incentives: Secondary analysis of the STEP UP randomized clinical trial.

Participants often vary in their response to behavioral interventions, but methods to identify groups of participants that are more likely to respond are lacking. In this secondary analysis of a randomized clinical trial, we used baseline characteristics to group participants into distinct behavioral phenotypes and evaluated differential responses to a physical activity intervention. Latent class analysis was used to segment participants based on baseline participant data including demographics, validated measures of psychosocial variables, and physical activity behavior. The trial included 602 adults from 40 U.S. states with body mass index ≥25 who were randomized to control or one of three gamification interventions (supportive, collaborative, or competitive) to increase physical activity. Daily step counts were monitored using a wearable device for a 24-week intervention with 12 weeks of follow-up. The model segmented participants into three classes named for key defining traits: Class 1, extroverted and motivated; Class 2, less active and less social; Class 3, less motivated and at-risk. Adjusted regression models were used to test for differences in intervention response relative to control within each behavioral phenotype. In Class 1, only participants in the competitive arm increased their mean daily steps during the intervention (adjusted difference, 945; 95% CI, 352-1537; P = .002), but it was not sustained during follow-up. In Class 2, participants in all three gamification arms significantly increased their mean daily steps compared to control during the intervention (supportive arm adjusted difference 1172; 95% CI, 363-1980; P = .005; collaborative arm adjusted difference 1119; 95% CI, 319-1919; P = .006; competitive arm adjusted difference 1179; 95% CI, 400-1957; P = .003) and all three had sustained impact during follow-up. In Class 3, none of the interventions had a significant effect on physical activity. Three behavioral phenotypes were identified, each with a different response to the interventions. This approach could be used to better target behavioral interventions to participants that are more likely to respond to them.