Biology subjects

Howard, J. A.

Publications and source records attributed to Howard, J. A..

3 recordsLinked to original sources

bioRxiv2024

Structural Basis of Non-Latent Signaling by the Anti-Mullerian Hormone Procomplex

Most TGF{beta} family ligands exist as procomplexes consisting of a prodomain noncovalently bound to a growth factor (GF); Whereas some prodomains confer latency, the Anti-Mullerian Hormone (AMH) prodomain maintains a remarkably high affinity for the GF yet remains active. Using single particle EM methods, we show the AMH prodomain consists of two subdomains: a vestigial TGF{beta} prodomain-like fold and a novel, helical bundle GF-binding domain, the result of an exon insertion 450 million years ago, that engages both receptor epitopes. When associated with the prodomain, the AMH GF is distorted into a strained, open conformation whose closure upon bivalent binding of AMHR2 displaces the prodomain through a conformational shift mechanism to allow for signaling.

molecular biology↗

bioRxiv2023

Heterogeneity in Neutrophil Extracellular Traps from Healthy Human Subjects

Neutrophil Extracellular Traps (NETs), a key component of early defense against microbial infection, are also associated with tissue injury. NET composition has been reported to vary with some disease states, but the composition and variability of NETs across many healthy subjects provides a critical comparison that has not been well investigated. We evaluated NETs from twelve healthy subjects of varying ages isolated from multiple blood draws over a three and one half-year period to delineate the variability in extracellular DNA, protein, enzymatic activities, and susceptibility to protease inhibitors. We calculated correlations for NET constituents and loss of human bronchial epithelial barrier integrity, measured by transepithelial electrical resistance, after NET exposure. We found that although there was some variability within the same subject over time, the mean numbers of neutrophils, protein, LDH, serine protease activities, and cytokines IL-8, IL-1RA, and G-CSF in isolated NETs were consistent across subjects. Total DNA and double stranded DNA content in NETs were different across donors. NETs had little or no TNF, IL-17A, or GM-CSF. NET DNA concentration correlated with increased NET neutrophil elastase activity and higher NET IL-1RA concentrations. NET serine protease activity varied considerably within the same donor from day-to-day. Mean response to protease inhibitors was significantly different across donors. NET DNA concentration correlated best with reductions in barrier integrity of human bronchial epithelia. Defining NET concentration by DNA content correlates with other NET components and reductions in NET-driven epithelial barrier dysfunction, suggesting DNA is a reasonable surrogate measurement for these complex structures in healthy subjects.

cell biology↗

bioRxiv2023

Activin E is a TGFβ ligand that signals specifically through activin receptor-like kinase 7.

Activins are one of the three distinct subclasses within the greater Transforming Growth Factor {beta} (TGF{beta}) superfamily. First discovered for their critical roles in reproductive biology, activins have since been shown to alter cellular differentiation and proliferation. At present, members of the activin subclass include activin A (ActA), ActB, ActC, ActE, and the more distant members myostatin and GDF11. While the biological roles and signaling mechanisms of most activins class members have been well-studied, the signaling potential of ActE has remained largely unknown. Here, we characterized the signaling capacity of homodimeric ActE. Molecular modeling of the ligand:receptor complexes showed that ActC and ActE shared high similarity in both the type I and type II receptor binding epitopes. ActE signaled specifically through ALK7, utilized the canonical activin type II receptors, ActRIIA and ActRIIB, and was resistant to the extracellular antagonists follistatin and WFIKKN. In mature murine adipocytes, ActE invoked a SMAD2/3 response via ALK7, similar to ActC. Collectively, our results establish ActE as an ALK7 ligand, thereby providing a link between genetic and in vivo studies of ActE as a regulator of adipose tissue. SignificanceActivin E is a homodimeric member of the TGF{beta} family belonging to the activin subclass. Currently, the signaling capacity of ActE is unknown due to a lack of reliable reagents to study the protein. Here, we demonstrate that ActE acts as a canonical TGF{beta} ligand that signals through SMAD2/3 in an ALK7-dependent manner, similar to ActC. ActE also utilizes the activin type II receptors, ActRIIA and ActRIIB, to signal and is unable to be antagonized by FS288 and WFIKKN2. This study shows that ActE is a signaling ligand and provides a connection between genetic and in vivo studies that links ActE to adiposity.

biochemistry↗