Biology subjects

Knapik, E. W.

Publications and source records attributed to Knapik, E. W..

3 recordsLinked to original sources

bioRxiv2025

Dynamic regulation of the COPII interactome and collagen trafficking by site-specific glycosylation of Sec24D

Coat protein complex II (COPII) mediates anterograde trafficking from the endoplasmic reticulum (ER). While the core COPII machinery is well-characterized, how cells regulate COPII to accommodate large cargoes, including collagens, remains incompletely understood. Here, we show that the cargo-selecting COPII subunit Sec24D is modified by site-specific O-linked {beta}-N-acetylglucosamine (O-GlcNAc) in its N-terminal intrinsically disordered region upon induction of collagen transport. These glycosylations are required for collagen trafficking in human cells and developing zebrafish. Crosslinking proteomics demonstrated that each O-GlcNAcylation influences the Sec24D interactome in a distinct way, revealing novel mediators of COPII function. In particular, Sec24D glycosylation is required for its interaction with myoferlin, which unexpectedly facilitates fusion of ER exit sites (ERES) and the ER-Golgi intermediate compartment (ERGIC) to enable collagen transport. Our results establish Sec24D O-GlcNAcylation as a dynamic regulator of COPII protein-protein interactions and collagen trafficking and identify myoferlin as a novel mediator of this process.

cell biology↗

bioRxiv2024

A non-muscle α-actinin is an intrinsic component of the cardiac Z-disc and regulates sarcomere turnover, contractility, and heart remodeling

Cardiac sarcomeres generate the fundamental forces behind each heartbeat and are thought to contain only muscle-specific cytoskeletal proteins. We show that a widely expressed actin cross-linking protein, -actinin 4 (ACTN4), is a sarcomere component of the human and zebrafish heart in vivo and in human iPSC-derived cardiac myocytes (CMs) in vitro. A confluence of biochemical experiments, immunofluorescence, and AI modeling suggest ACTN4 forms a heterodimeric complex with muscle-specific ACTN2 at the cardiac Z-disc, the cardiac sarcomere border. ACTN4 depletion from human iPSC-CMs stabilizes canonical sarcomere proteins and drives contractility-dependent cellular hypertrophy while ACTN4 overexpression destabilizes sarcomeres. ACTN4 depletion from zebrafish embryos specifically increases ventricular contractility which drives atrial enlargement, suggesting biomechanically driven atrial remodeling. ACTN4-associated phenotypes in both model systems lack hallmarks of cardiac disease models and an ACTN4 variant in humans is associated with reduced risk for disease. Our findings suggest a "non-muscle" actinin regulates heart contractility and influences clinical outcomes related to heart failure.

cell biology↗

bioRxiv2022

Regulated extracellular matrix trafficking shapes cell growth during cartilage morphogenesis

Craniofacial malformations are present in more than one third of all congenital syndromes, but the pathogenesis of skeletal dysmorphology is poorly understood. Here, using an unbiased forward genetics approach in zebrafish, we identified a mutation in erc1b that leads to craniofacial defects, including micrognathia and hypertelorism caused by impaired cartilage and bone growth. To date, ERC1 has not been considered a candidate gene for craniofacial syndromes. Using live in vivo imaging, genetic depletion and replacement experiments, and transgenic approaches, we interrogated erc1b function. We found that Erc1b regulates extracellular matrix (ECM) trafficking required for the highly conserved "stack of coins" organization of chondrocytes in cartilage that is essential for skeletal growth and integrity. Erc1b functions cellautonomously at the chondrocyte cell cortex to regulate traffic of ECM and plasma membrane expansion in a microtubule dependent manner during isometric cell growth. Disruption of Erc1-Rab8-Kinesin-1 axis leads to failure of cartilage maturation, endochondral bone formation and ultimately chondrocyte cell death. Our study identifies Erc1b as a candidate genetic factor for craniofacial syndromes.

developmental biology↗