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All Publications

  • Understanding the molecular basis of HCM-causing mutations in cardiac myosin and cardiac myosin binding protein-C Pathak, D., Nandwani, N., Ruppel, K., Spudich, J. A. CELL PRESS. 2022: 255A
  • Patient Perspectives of Inpatient Telemedicine During COVID-19: A Qualitative Assessment. JMIR formative research Vilendrer, S., Sackeyfio, S., Akinbami, E., Ghosh, R., Luu, J. H., Pathak, D., Shimada, M., Williamson, E. E., Shieh, L. 2022


    Telemedicine has been adopted in the inpatient setting to facilitate clinical interactions between on-site clinicians and isolated hospitalized patients. Such remote interactions have the potential to reduce pathogen exposure and use of personal protective equipment but may also pose new safety concerns given prior evidence that isolated patients can receive suboptimal care. Formal evaluations into the use and practical acceptance of inpatient telemedicine amongst hospitalized patients are lacking.We aimed to evaluate the experience of patients hospitalized for COVID-19 with inpatient telemedicine introduced as an infection control measure during the pandemic.We conducted a qualitative evaluation in a COVID-19 designated non-intensive care hospital unit at a large academic health center (Stanford Health Care) October 2020 through January 2021. Semi-structured qualitative interviews focused on patient experience, impact on quality of care, communication, and mental health. Purposive sampling were used to recruit participants represent-ing diversity across varying demographics until thematic saturation was reached. Interview transcripts were qualitatively analyzed using an inductive-deductive approach.Interviews with 20 hospitalized patients suggested non-emergency clinical care and bridging to in-person care comprised the majority of inpatient telemedicine use. Nurses were reported to enter the room and call on the tablet far more frequently than physicians, who typically entered the room at least daily. Patients reported broad acceptance of the technology, citing improved convenience and reduced anxiety but preferred in-person care where possible. Quality of care was believed to be similar to in-person care with the exception of a few patients who wanted more frequent in-person examinations. Ongoing challenges included low volume, shifting tablet location, and inconsistent verbal introductions from the clinical team.Patient experiences with in-patient telemedicine were largely favorable. Although most patients ex-pressed a preference for in-person care, telemedicine was acceptable given the circumstances asso-ciated with COVID-19. Technical and care team use improvements may enhance acceptability. Fur-ther evaluation is needed to understand the impact of inpatient telemedicine and the optimal balance between in-person and virtual care in the hospital setting.

    View details for DOI 10.2196/32933

    View details for PubMedID 35147510

  • Nanomechanical Phenotypes in Cardiac Myosin-Binding Protein C Mutants That Cause Hypertrophic Cardiomyopathy. ACS nano Suay-Corredera, C., Pricolo, M. R., Velazquez-Carreras, D., Pathak, D., Nandwani, N., Pimenta-Lopes, C., Sanchez-Ortiz, D., Urrutia-Irazabal, I., Vilches, S., Dominguez, F., Frisso, G., Monserrat, L., Garcia-Pavia, P., de Sancho, D., Spudich, J. A., Ruppel, K. M., Herrero-Galan, E., Alegre-Cebollada, J. 2021


    Hypertrophic cardiomyopathy (HCM) is a disease of the myocardium caused by mutations in sarcomeric proteins with mechanical roles, such as the molecular motor myosin. Around half of the HCM-causing genetic variants target contraction modulator cardiac myosin-binding protein C (cMyBP-C), although the underlying pathogenic mechanisms remain unclear since many of these mutations cause no alterations in protein structure and stability. As an alternative pathomechanism, here we have examined whether pathogenic mutations perturb the nanomechanics of cMyBP-C, which would compromise its modulatory mechanical tethers across sliding actomyosin filaments. Using single-molecule atomic force spectroscopy, we have quantified mechanical folding and unfolding transitions in cMyBP-C domains targeted by HCM mutations that do not induce RNA splicing alterations or protein thermodynamic destabilization. Our results show that domains containing mutation R495W are mechanically weaker than wild-type at forces below 40 pN and that R502Q mutant domains fold faster than wild-type. None of these alterations are found in control, nonpathogenic variants, suggesting that nanomechanical phenotypes induced by pathogenic cMyBP-C mutations contribute to HCM development. We propose that mutation-induced nanomechanical alterations may be common in mechanical proteins involved in human pathologies.

    View details for DOI 10.1021/acsnano.1c02242

    View details for PubMedID 34060810

  • Lipidomics Suggests a New Role for Ceramide Synthase in Phagocytosis ACS CHEMICAL BIOLOGY Pathak, D., Mehendale, N., Singh, S., Mallik, R., Kamat, S. S. 2018; 13 (8): 2280-2287


    Phagocytosis is an evolutionarily conserved biological process where pathogens or cellular debris are cleared by engulfing them in a membrane-enclosed cellular compartment called the phagosome. The formation, maturation, and subsequent degradation of a phagosome is an important immune response essential for protection against many pathogens. Yet, the global lipid profile of phagosomes remains unknown, especially as a function of their maturation in immune cells. Here, we show using mass spectrometry based quantitative lipidomics that the ceramide class of lipids, especially very long chain ceramides, are enriched on maturing phagosomes with a concomitant decrease in the biosynthetic precursors of ceramides. We thus posit a new function for the enzyme ceramide synthase during phagocytosis in mammalian macrophages. Biochemical assays, cellular lipid feeding experiments, and pharmacological blockade of ceramide synthase together show that this enzyme indeed controls the flux of ceramides on maturing phagosomes. We also find similar results in the primitive eukaryote Dictyostelium discoideum, suggesting that ceramide enrichment may be evolutionarily conserved and likely an indispensible step in phagosome maturation.

    View details for DOI 10.1021/acschembio.8b00438

    View details for Web of Science ID 000442452300045

    View details for PubMedID 29963848

    View details for PubMedCentralID PMC6102644

  • Lipid - Motor Interactions: Soap Opera or Symphony? CURRENT OPINION IN CELL BIOLOGY Pathak, D., Mallik, R. 2017; 44: 79-85


    Intracellular transport of organelles can be driven by multiple motor proteins that bind to the lipid membrane of the organelle and work as a team. We review present knowledge on how lipids orchestrate the recruitment of motors to a membrane. Looking beyond recruitment, we also discuss how heterogeneity and local mechanical properties of the membrane may influence function of motor-teams. These issues gain importance because phagocytosed pathogens use lipid-centric strategies to manipulate motors and survive in host cells.

    View details for DOI 10.1016/

    View details for Web of Science ID 000400022400012

    View details for PubMedID 27697416

  • Dynein Clusters into Lipid Microdomains on Phagosomes to Drive Rapid Transport toward Lysosomes CELL Rai, A., Pathak, D., Thakur, S., Singh, S., Dubey, A., Mallik, R. 2016; 164 (4): 722-734


    Diverse cellular processes are driven by motor proteins that are recruited to and generate force on lipid membranes. Surprisingly little is known about how membranes control the force from motors and how this may impact specific cellular functions. Here, we show that dynein motors physically cluster into microdomains on the membrane of a phagosome as it matures inside cells. Such geometrical reorganization allows many dyneins within a cluster to generate cooperative force on a single microtubule. This results in rapid directed transport of the phagosome toward microtubule minus ends, likely promoting phagolysosome fusion and pathogen degradation. We show that lipophosphoglycan, the major molecule implicated in immune evasion of Leishmania donovani, inhibits phagosome motion by disrupting the clustering and therefore the cooperative force generation of dynein. These findings appear relevant to several pathogens that prevent phagosome-lysosome fusion by targeting lipid microdomains on phagosomes.

    View details for DOI 10.1016/j.cell.2015.12.054

    View details for Web of Science ID 000369998300017

    View details for PubMedID 26853472

    View details for PubMedCentralID PMC4752818