Biology subjects

Beckmann, H.

Publications and source records attributed to Beckmann, H..

3 recordsLinked to original sources

bioRxiv2023

Acute stress modulates social approach and social maintenance in adult zebrafish

Stress alters social functioning in a complex manner. An important variable determining the final effects of stress is stressor intensity. However, the precise relationship between stressor intensity and social behavior is not well understood. Here we investigate the effects of varying acute stressor intensity exposure on social behavior using adult zebrafish. We first establish a novel test using adult zebrafish that allows distinguishing fishs drive to approach a social cue and its ability to engage and maintain social interaction within the same behavioral paradigm. Next, we combined this test with a new method to deliver an acute stress stimulus of varying intensities. Our results show that both social approach and social maintenance are reduced in adult zebrafish upon acute stress exposure in an intensity-dependent manner. Interestingly, lower stress intensity reduces social maintenance without affecting the social approach, while a higher stress level is required to alter social approach. These results provide evidence for a direct correlation between acute stressor intensity and social functioning and suggest that distinct steps in social behavior are modulated differentially by the acute stress level. SIGNIFICANCE STATEMENTAcute stress exposure has a potent effect on social behavior in many animals including humans. However, so far the effect of different stressor intensity on distinct steps of social behavior has not been directly tested. Here, using zebrafish, we develop a new social behavior paradigm and a new graded acute stressor delivery method in order to test the relationship between acute stressor intensity and social behavior. Our results show that acute stress modulates both social approach and social maintenance in an intensity-dependent manner but social maintenance is affected at lower stress intensity than social approach. Thus, this work reveals that distinct steps in social behavior are differentially modulated by the acute stress level.

neuroscience↗

bioRxiv2021

Heterodimers of functionally divergent ARF-GEF paralogues prevented by self-interacting dimerisation domain

Functionally divergent paralogs of homomeric proteins do not form potentially deleterious heteromers, which requires distinction between self and non-self (Hochberg et al., 2018; Marchant et al, 2019; Marsh and Teichmann, 2015). In Arabidopsis, two ARF guanine-nucleotide exchange factors (ARF-GEFs) related to mammalian GBF1, named GNOM and GNL1, can mediate coatomer complex (COPI)-coated vesicle formation in retrograde Golgi-endoplasmic reticulum (ER) traffic (Geldner et al., 2003; Richter et al., 2007; Teh and Moore, 2007). Unlike GNL1, however, GNOM is also required for polar recycling of endocytosed auxin efflux regulator PIN1 from endosomes to the plasma membrane. Here we show that these paralogues form homodimers constitutively but no heterodimers. We also address why and how GNOM and GNL1 might be kept separate. These paralogues share a common domain organisation and each N-terminal dimerisation (DCB) domain can interact with the complementary fragment ({Delta}DCB) of its own and the other protein. However, unlike self-interacting DCBGNOM (Grebe et al., 2000; Anders et al., 2008), DCBGNL1 did not interact with itself nor DCBGNOM. DCBGNOM removal or replacement with DCBGNL1, but not disruption of cysteine bridges that stabilise DCB-DCB interaction, resulted in GNOM-GNL1 heterodimers which impaired developmental processes such as lateral root formation. We propose precocious self-interaction of the DCBGNOM domain as a mechanism to preclude formation of fitness-reducing GNOM-GNL1 heterodimers.

plant biology↗

bioRxiv2020

ARF1 dimerization is essential for vesicle trafficking and dependent on activation by ARF-GEF dimers in Arabidopsis

Membrane traffic maintains the organization of the eukaryotic cell and delivers cargo proteins to their subcellular destinations such as sites of action or degradation. Membrane vesicle formation requires ARF GTPase activation by the SEC7 domain of ARF guanine-nucleotide exchange factors (ARF-GEFs), resulting in the recruitment of coat proteins by GTP-bound ARFs. In vitro exchange assays were done with monomeric proteins, although ARF-GEFs have been shown to form dimers in vivo. This feature is conserved across the eukaryotes, however its biological significance is unknown. Here we demonstrate ARF1 dimerization in vivo and we show that ARF-GEF dimers mediate ARF1 dimer formation. Mutational disruption of ARF1 dimers interfered with ARF1-dependent trafficking but not coat protein recruitment in Arabidopsis. Mutations disrupting simultaneous binding of two ARF1*GDPs by the two SEC7 domains of GNOM ARF-GEF dimer prevented stable interaction of ARF1 with ARF-GEF and thus, efficient ARF1 activation. Our results suggest a model of activation-dependent dimerization of membrane-inserted ARF1*GTP molecules required for coated membrane vesicle formation. Considering the evolutionary conservation of ARFs and ARF-GEFs, this initial regulatory step of membrane trafficking might well occur in eukaryotes in general.

plant biology↗