CD49d governs immune synapse formation through actin rearrangements and synchronizes BCR signaling in CLL
Abstract
Abstract B-cell receptor (BCR) signaling is a key determinant of chronic lymphocytic leukemia (CLL) pathophysiology. CD49d, the α4 subunit of the very late antigen 4 integrin, can be activated by BCR signals; however, its role in modulating BCR functionality remains unknown. We used knockout mouse models and primary human CLL stratified by CD49d expression to address this aspect. CD49d was required for bone marrow (BM) infiltration and shaped BM infiltration patterns and patient outcomes in human CLL. In TCL1 transplantation models, the loss of CD49d abrogated BM homing and leukemic cell positioning within splenic niches. At the cellular level, CD49d-deficient murine TCL1 transgenic cells and human CD49d-low CLL cells failed to form efficient immune synapses with antigen-presenting membranes. Transcriptome analyses identified CD49d-dependent regulation of actin-associated pathways and distinct signatures of BCR responsiveness in both human and mouse cells. Consistently, CD49d-low human CLL cells displayed aberrant actin remodeling following BCR stimulation, and a second aggressive murine CLL model reproduced the actin and engraftment defects. Kinome profiling linked impaired antigen-induced BCR responses in CD49d-deficient murine cells to altered kinase activity, and pharmacologic actin perturbation phenocopied CD49d loss. In human CD49d-low CLL cells, a desynchronization of BCR-related downstream Syk and PLCɣ2 activation was found. Mechanistically, the CD49d-BCR interplay involved their colocalization, and CD49d converged with BCR signaling on a focal adhesion kinase–actin axis. In summary, our findings establish CD49d as a key regulator of BCR functionality in CLL, linking integrins to cytoskeletal dynamics and antigen responsiveness.
Article Details
Authors (34)
Laura Polcik
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
Abhishek Pethe
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
Driti Ashok
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
Erika Tissino
3Clinical and Experimental Onco-Hematology Unit, Centro di Riferimento Oncologico di Aviano, Istituto di Ricovero e Cura a Carattere Scientifico, Aviano, Italy
Adrián Fernández-Rego
4Department of Immunology & Oncology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas, Madrid, Spain
Federico Pozzo
3Clinical and Experimental Onco-Hematology Unit, Centro di Riferimento Oncologico di Aviano, Istituto di Ricovero e Cura a Carattere Scientifico, Aviano, Italy
Danielle-Justine Danner
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
Manuel Holst
Claudio Martines
Karin Hofmann
7Molecular Hematology Unit, International Center for Genetic Engineering and Biotechnology, Trieste, Italy
Aleksandar J. Dimovski
8Macedonian Academy of Sciences and Arts, Skopje, North Macedonia
Sandra Kissel
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
Andrea Härzschel
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
Lixia Li
Tamara Bittolo
3Clinical and Experimental Onco-Hematology Unit, Centro di Riferimento Oncologico di Aviano, Istituto di Ricovero e Cura a Carattere Scientifico, Aviano, Italy
Geoffroy Andrieux
Theresa Haslauer
10Department of Internal Medicine III with Hematology, Medical Oncology, Hemostaseology, Infectiology and Rheumatology, Oncologic Center, Salzburg Cancer Research Institute-Laboratory for Immunological and Molecular Cancer Research, Cancer Cluster Salzburg, Paracelsus Medical University, Salzburg, Austria
Jan Philip Höpner
10Department of Internal Medicine III with Hematology, Medical Oncology, Hemostaseology, Infectiology and Rheumatology, Oncologic Center, Salzburg Cancer Research Institute-Laboratory for Immunological and Molecular Cancer Research, Cancer Cluster Salzburg, Paracelsus Medical University, Salzburg, Austria
Nadja Zaborsky
Richard Greil
Cornelius Miething
Department of Medicine I, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany, Freiburg, Germany
Jesus Duque-Afonso
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
Natalie Köhler
Melanie Boerries
Riccardo Bomben
3Clinical and Experimental Onco-Hematology Unit, Centro di Riferimento Oncologico di Aviano, Istituto di Ricovero e Cura a Carattere Scientifico, Aviano, Italy
Justus Duyster
Robert Grosse
Gianluca Gaidano
13Department of Translational Medicine, University of Eastern Piedmont, Novara, Italy
Alberto Zamò
14Institute of Pathology, University of Würzburg, Würzburg, Germany
Antonella Zucchetto
3Clinical and Experimental Onco-Hematology Unit, Centro di Riferimento Oncologico di Aviano, Istituto di Ricovero e Cura a Carattere Scientifico, Aviano, Italy
Yolanda R. Carrasco
4Department of Immunology & Oncology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas, Madrid, Spain
Dimitar G. Efremov
7Molecular Hematology Unit, International Center for Genetic Engineering and Biotechnology, Trieste, Italy
Valter Gattei
3Clinical and Experimental Onco-Hematology Unit, Centro di Riferimento Oncologico di Aviano, Istituto di Ricovero e Cura a Carattere Scientifico, Aviano, Italy
Tanja Nicole Hartmann
1Department of Medicine I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany