Biology subjects

Schmidt, F. I.

Publications and source records attributed to Schmidt, F. I..

2 recordsLinked to original sources

bioRxiv2020

Nanobody-directed targeting of optogenetic tools reveals differential regulation of cilia length

Compartmentalization of cellular signaling forms the molecular basis of cellular behavior. The primary cilium constitutes a subcellular compartment that orchestrates signal transduction independent from the cell body. Ciliary dysfunction causes severe diseases, termed ciliopathies. Analyzing ciliary signaling and function has been challenging due to the lack of tools to temporarily manipulate and analyze ciliary signaling. Here, we describe a nanobodybased targeting approach for optogenetic tools that is applicable in vitro and in vivo and allows to specifically analyze ciliary signaling and function. Thereby, we overcome the loss of protein function observed after direct fusion to a ciliary targeting sequence. We functionally localized modifiers of cAMP signaling, i.e. the photo-activated adenylate cyclase bPAC and the light-activated phosphodiesterase LAPD, as well as the cAMP biosensor mlCNBD-FRET to the cilium. Using this approach, we studied the contribution of spatial cAMP signaling in controlling cilia length. Combining optogenetics with nanobody-based targeting will pave the way to the molecular understanding of ciliary function in health and disease.

cell biology↗

bioRxiv2020

ASC oligomer favor caspase-1CARD domain recruitment after intracellular potassium efflux

Signaling through the inflammasome is important for the inflammatory response. Low concentrations of intracellular K+ are associated with the specific oligomerization and activation of the NLRP3 inflammasome, a type of inflammasome involved in sterile inflammation. Subsequent to NLRP3 oligomerization, ASC protein binds and form oligomeric filaments culminating in large protein complexes named ASC specks. ASC specks are also initiated from different inflammasome scaffolds, as AIM2, NLRC4 or Pyrin. ASC oligomers induce the recruitment of caspase-1 through interactions between their respective caspase activation and recruitment domains (CARD), and favoring its activation. So far ASC oligomerization and caspase-1 activation are considered as a K+-independent process. Here we found that ASC oligomers change their structure upon low intracellular K+ independently of NLRP3 and allow the ASCCARD domain to be more accessible for the recruitment of pro-caspase-1CARD domain. Therefore, conditions that decrease intracellular K+ not only drive NLRP3 responses, but also enhance the recruitment of pro-caspase-1 by ASC specks formed by different inflammasomes, indicating that intracellular K+ homeostasis is a key regulatory step for inflammasome regulation.

immunology↗