Biology subjects

Kreienkamp, H.-J.

Publications and source records attributed to Kreienkamp, H.-J..

3 recordsLinked to original sources

bioRxiv2021

Mutations affecting the N-terminal domains of SHANK3 point to different pathomechanisms in neurodevelopmental disorders.

Shank proteins are major scaffolds of the postsynaptic density of excitatory synapses. Mutations in SHANK genes are associated with autism and intellectual disability. The relevance of missense mutations for these pathologies is unclear. Several missense mutations in SHANK3 affect the N-terminal region, consisting of the Shank/ProSAP N-terminal (SPN) domain and a set of Ankyrin (Ank) repeats. Here we identify a novel SHANK3 missense mutation (p.L270M) in the Ankyrin repeats in patients with an ADHD-like phenotype. We functionally analysed this and a series of other mutations, using biochemical and biophysical techniques. We observe two major effects: (i) a loss of binding to {delta}-catenin (e.g. in the p.L270M variant), and (ii) interference with the intramolecular interaction between N-terminal SPN domain and the Ank repeats. This also interferes with binding to the -subunit of the calcium-/calmodulin dependent kinase II (CaMKII), and appears to be associated with a more severe neurodevelopmental pathology.

neuroscience↗

bioRxiv2021

Autism associated SHANK3 missense point mutations impact conformational fluctuations and protein turnover at synapses

Members of the SH3- and ankyrin-rich repeat (SHANK) protein family are considered as master scaffolds of the post-synaptic density of glutamatergic synapses. Several missense mutations within the canonical SHANK3 isoform have been proposed as causative for the development of autism spectrum disorders (ASDs). However, there is a surprising paucity of data linking missense mutation-induced changes in protein structure and dynamics to the occurrence of ASD-related synaptic phenotypes. In this work, we focus on two ASD-associated point mutations, both located within the same domain of SHANK3. In a proof-of-principle study we demonstrate that both mutant proteins show indeed distinct changes in secondary and tertiary structure as well as higher conformational fluctuations. Local and surprisingly also distal structural disturbances of protein folding result in altered synaptic targeting and changes of protein turnover at synaptic sites.

neuroscience↗

bioRxiv2020

Conformational dynamics regulate SHANK3 actin and Rap1 binding

Actin-rich cellular protrusions direct versatile biological processes from cancer cell invasion to dendritic spine development. The stability, morphology and specific biological function of these protrusions are regulated by crosstalk between three main signaling axes: integrins, actin regulators and small GTPases. SHANK3 is a multifunctional scaffold protein, interacting with several actin-binding proteins, and a well-established autism risk gene. Recently, SHANK3 was demonstrated to sequester integrin-activating small GTPases Rap1 and R-Ras to inhibit integrin activity via its N-terminal SPN domain. Here, we demonstrate that SHANK3 interacts directly with actin using its SPN domain. Actin binding can be inhibited by an intramolecular closed conformation of SHANK3, where the adjacent ARR domain covers the actin-binding interface of the SPN domain. Actin and Rap1 compete with each other for binding to SHANK3 and loss of SHANK3-actin binding augments inhibition of Rap1-mediated integrin activity. This dynamic crosstalk has functional implications for filopodia formation in cancer cells, dendritic spine morphology in neurons and autism-linked phenotypes in vivo.

cell biology↗