Microtubule anchoring and coupling of CD20 to the RhoA/Rock1 pathway (PKCdelta KO SILAC phosphoproteomics)

ABSTRACT: CD20 is a B cell-specific four-helix transmembrane protein and a prominent target of successful therapeutic anti-CD20 antibodies such as rituximab (RTX) and GA101. We have recently described that CD20 is localized within a membrane nanocluster harboring the IgD class B cell antigen receptor (IgD-BCR) where it functions as a gatekeeper for the resting state of naïve human B lymphocytes. Loss of CD20 results in the remodeling of the IgD-BCR nanocluster and B cell activation. How CD20 exerts its gatekeeper function was not known so far. Using the Ramos B cell system and human peripheral blood B cells, we show here that another B cell gatekeeper, the serine/threonine kinase PKCδ, constitutively phosphorylates specific serine residues at the N- and C-terminal cytosolic tails of CD20. The phosphorylated CD20 becomes a target for 14-3-3 adaptor proteins that link CD20 to the RhoA GDP/GTP exchange factor GEF-H1 (ARHG2). The autoinhibited form of GEF-H1 couples CD20 to the microtubule network that controls the stability of the IgD-BCR nanocluster on resting B cells. Binding of anti-CD20 antibodies results in microtubule disassembly and the replacement of the GEF-H1/CD20 complex by a RhoA-GTP/ROCK1/CD20 complex, which drives actomyosin assembly and translocation of CD20 and the coreceptor CD19 to the IgM-BCR. The effect of anti-CD20 antibodies can be mimicked by exposing B cells to microtubule destabilizing drugs such as nocodazole (Noc) whereas microtubule stabilizing drugs such as Taxol (Tax) prevent the IgD-BCR nanocluster dissociation a finding that may alter therapeutic protocols of anti-CD20 treatments. Taken together, our study suggests that CD20 not only maintains the resting state, but also orchestrates the microtubule-actin switch in active B lymphocytes.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): B Cell, Cell Culture

SUBMITTER: Julian Bender  

LAB HEAD: Bettina Warscheid

PROVIDER: PXD063667 | Pride | 2026-04-17

REPOSITORIES: Pride