Dali, S. | bioRxiv Science

bioRxiv2024

Human medial pulvinar is involved in face and tactile processing and dynamically adjusts its cortical connectivity based on ongoing stimulation

Optimal processing of our surrounding environment relies on our ability to detect and integrate external information through multiple sensory modalities to build a coherent representation of the world. Interactions between cortical and subcortical structures contribute to this process. In this context, there is growing evidence that the pulvinar plays a crucial role in visual and face processing. In contrast, its role in auditory, voice and tactile processing has been poorly investigated. Here, we use fMRI localizer tasks to describe pulvinar functional organization and functional connectivity with the brain during face, voice and tactile processing. We reproduce the activation of the ventral part of the medial pulvinar in face perception and we describe an increased pulvinar connectivity with face processing areas and a decreased connectivity with low level visual areas during face processing. In addition, we describe activations of the medial pulvinar during air-puff face, hands and feet tactile stimulations and changes in pulvino-cortical connectivity as a function of which body part is being stimulated. No activations are observed during either voice or non-voice stimulations. Overall, this supports a role of medial pulvinar in multisensory processing and the modulation of cortical areas as a function of the sensory context.

neuroscience↗

bioRxiv2024

The fungal protein Jps1 facilitates unconventional protein secretion through a direct phosphoinositide interaction

Protein secretion is indispensable for essential cellular processes in eukaryotic cells, contributing significantly to nutrient acquisition, defense or communication. Alternative pathways bypassing the endomembrane system collectively referred to as unconventional secretion are gaining increasing attention. A number of important molecules such as cytokines, fibroblast growth factor or viral proteins are being exported through these mechanistically diverse pathways. In the fungal model Ustilago maydis, cytokinesis-dependent unconventional secretion mediates export of the chitinase Cts1 via the fragmentation zone. This membrane-rich compartment is formed during cytokinesis between mother and daughter cells. Recently, we identified Jps1, a previously uncharacterized protein, as a crucial factor for Cts1 localization and export. Combining biochemical experiments and in vivo studies, we here uncover two pivotal features of Jps1: dimerization and phosphoinositide (PIP) binding. Our findings reveal that a conserved structural core domain mediates homodimerization, while surrounding flexible variable regions suggest potential diversification in different basidiomycete species. Jps1 does not harbor a canonical PIP-binding domain but instead specificity of the interaction with the preferred PIP PI(4,5)P2 is determined by basic residues. Importantly, loss of PI(4,5)P2 binding specificity results in mis-localisation, morphological defects and reduced extracellular Cts1 activity, particularly at low cell densities. This discovery sheds light on previously unknown key features of Jps1, elucidating its role in supporting Cts1 secretion, and representing a crucial step towards understanding the broader implications of unconventional secretion in eukaryotic cells.

biochemistry↗