Biology subjects

Buss, F.

Publications and source records attributed to Buss, F..

3 recordsLinked to original sources

bioRxiv2025

Plasmodium falciparum Myosin F with a Rab-like tail domain localises to perinuclear membranes and associates with trafficking proteins

Members of the myosin superfamily are found in all eukaryotes, including Plasmodium falciparum, the parasite that causes malaria. Plasmodium falciparum expresses six myosins, but apart from PfMyoA, these motors remain largely uncharacterised. This includes the class XXII myosin PfMyoF. Here, we characterise PfMyoF using structural prediction tools, biochemical assays, and advanced imaging. We show that PfMyoF is a plus-end directed, processive motor with a long neck domain containing six IQ motifs that bind the calmodulin homologue PfCaM. PfMyoF can dimerise and is predicted to adopt an autoinhibited conformation via tail backfolding. The PfMyoF tail contains a Rab-like domain that has not been identified in any other known class of myosin. Pull-down experiments show interactions between endogenous PfMyoF and trafficking proteins, including the vesicle marker PfRab18. Expansion and immunoelectron microscopy reveal that PfMyoF localises to a perinuclear membrane compartment. Our findings define PfMyoF as the first known myosin with a Rab-like domain and highlight its potential role in parasite membrane trafficking pathways.

molecular biology↗

bioRxiv2025

MYO1F interactome reveals the SH3-domain linked CASS complex at podosomes and the phagocytic cup

MYO1F, a long-tailed myosin of class I, is selectively expressed in immune cells and upregulated in microglia associated with neurodegenerative pathogenesis. The intracellular functions of myosin motors involve adaptor proteins, which regulate cargo attachment and intracellular motor recruitment. To define the MYO1F interactome, we performed an in situ proximity labelling-based proteomic analysis in human myeloid U937 cells. We identified a distinct SH3-domain-dependent adaptor module comprising CD2AP, ASAP1, SH3BP2, and SH3KBP1 (CASS complex), which localizes with MYO1F in podosomes and phagocytic cups. Structural modelling and mutagenesis confirmed multivalent proline-rich motif interactions of the CASS complex with the MYO1F SH3 domain. Further deletions revealed a second group of membrane-associated adaptor proteins that bind to the MYO1F pleckstrin homology (PH) domain. Immunofluorescence in macrophages and microglia confirmed the conserved localization of MYO1F and its adaptors at actin-rich podosomes and phagocytic cups. Functional assays demonstrated that MYO1F recruitment to the phagocytic cup requires motor activity and intact PH and SH3 domains. This study provides the first comparative interactome of MYO1F and its paralogue MYO1E and supports a role for MYO1F in podosomes and during phagocytosis in both peripheral and brain-resident myeloid cells.

cell biology↗

bioRxiv2019

OPTN translocates to an ATG9A-positive compartment to regulate innate immune signalling and cytokine secretion

Optineurin (OPTN) is a multifunctional protein involved in autophagy, secretion as well as NF-{kappa}B and IRF3 signalling and mutations are associated with several human diseases including primary open-angle glaucoma (POAG), amyotrophic lateral sclerosis (ALS), Pagets disease of bone (PDB) and Crohns disease (CD). Here we show that, in response to viral RNA, OPTN translocates to foci in the perinuclear region, where it negatively regulates NF-{kappa}B and IRF3 signalling pathways and downstream pro-inflammatory cytokine secretion. These OPTN foci consist of a tight cluster of small membrane vesicles, which are positive for marker proteins of the trans-Golgi network/recycling compartment - most notably ATG9A. Disease mutations linked to POAG cause aberrant formation of this compartment in the absence of stimuli, which correlates with the ability of OPTN to inhibit signalling. Using proximity labelling proteomics (BioID), we identify the linear ubiquitin assembly complex (LUBAC), CYLD and TBK1 as part of the OPTN interactome and show that these proteins, along with NEMO, are recruited to this OPTN-positive perinuclear compartment. Together, we propose OPTN might be responsible for dampening the NF-{kappa}B and IRF3 signalling responses through the sequestration of LUBAC and other positive regulators of these pathways in this dsRNA-induced compartment leading to altered pro-inflammatory cytokine secretion.\n\nSummaryDisease associated OPTN mutations impact on the formation of the perinuclear compartment and result in hypo- or hyper-activation of the immune response, which could drive the development of human diseases such as POAG, ALS and also Pagets disease of bone.

cell biology↗