Biology subjects

Strickland, D. K.

Publications and source records attributed to Strickland, D. K..

3 recordsLinked to original sources

bioRxiv2025

The Ligand Preference of LRP1 is Regulated by O-glycans

Low-density lipoprotein receptor (LDLR) and LDLR-related proteins (LRPs) are endocytic receptors serving as essential physiological regulators of multiple processes including cholesterol clearance, protein reabsorption and neuronal protein trafficking. We originally discovered O-glycans in linkers of the ligand-binding domains of LDLR/LRP receptors and showed that these play critical roles for uptake of LDL by LDLR and albumin by LRP2. Remarkably, these linker O-glycans are introduced exclusively by GALNT11, one out of 20 polypeptide GalNAc-transferase isoenzymes. Here, we investigate the role of linker O-glycans on the large ([~]600 kDa) and widely expressed multiligand LRP1 receptor implicated in diseases including neuropathies. In genetically engineered cell models we activated endogenous full-coding LRP1 with and without O-glycans and demonstrate that while the uptake of certain ligands, such as RAP and ApoE, was unaffected by O-glycans, the uptake of the neurotoxic molecules tau and amyloid beta was altered and in opposite directions. This demonstrates that O-glycans in ligand-binding domains can differentially modulate ligand affinity and specificity of LRP1. Our findings highlight an overlooked regulatory mechanism of endocytic receptors and identify the ligand repertoire of LRP1 as being influenced by O-glycans, with potential implications for neurodegenerative disease.

molecular biology↗

bioRxiv2025

Molecular determinants of extracellular TIMP-3 accumulation in Sorsby fundus dystrophy.

Tissue inhibitor of metalloproteinases-3 (TIMP-3) is a critical regulator of extracellular matrix turnover. Mutations in TIMP-3 cause Sorsby fundus dystrophy (SFD), an inherited macular dystrophy that is similar to age-related macular degeneration (AMD) but which generally presents earlier. SFD is characterised by the accumulation of mutant TIMP-3 protein in Bruchs membrane, a multilaminar extracellular matrix underlying the retinal pigment epithelium (RPE). Here, we show that RPE cells regulate wild-type TIMP-3 levels post-translationally, with ARPE-19 and hTERT RPE-1 cell lines endocytosing the protein via the low-density lipoprotein receptor-related protein (LRP) family of scavenger receptors. LRP-mediated endocytosis of the SFD TIMP-3 variants S204C and Y191C was significantly delayed, establishing a molecular mechanism for their extracellular accumulation in SFD. In contrast, endocytosis of the SFD variant H181R TIMP-3 was unaltered, suggesting it accumulates through a distinct molecular mechanism, potentially via increased retention on extracellular matrix heparan sulfate proteoglycans. These findings reveal heterogeneity in the molecular mechanism of SFD pathogenesis, which has direct implications for therapeutic development. Genotype-specific interventions may be required, such as strategies that enhance receptor-mediated clearance or disrupt extracellular TIMP-3 retention. Our study also has broader implications for AMD, where TIMP-3 and other LRP and heparan sulfate ligands accumulate in drusen within Bruchs membrane. Age- and inflammation-dependent alterations in LRP expression and heparan sulfate structure may contribute to drusen formation and AMD progression. Understanding TIMP-3 trafficking in both physiological and pathological contexts could inform targeted treatments for SFD, AMD, and other degenerative disorders involving extracellular matrix dysregulation.

biochemistry↗

bioRxiv2024

PAI-1 Interaction with Sortilin Related Receptor-1 is Required for Lung Fibrosis

Plasminogen activator inhibitor-1 (PAI-1) has been previously shown to promote lung fibrosis via a mechanism that requires an intact vitronectin (VTN) binding site. In the present study, employing two distinct murine fibrosis models, we find that VTN is not required for PAI-1 to drive lung scarring. This result suggested the existence of a previously unrecognized profibrotic PAI-1-protein interaction involving the VTN-binding site for PAI-1. Using an unbiased proteomic approach, we identified sortilin related receptor 1 (SorlA) as the most highly enriched PAI-1 interactor in the fibrosing lung. We next investigated the role of SorlA in pulmonary fibrosis and found that SorlA deficiency protected against lung scarring in a murine model. We further show that, while VTN deficiency does not influence fibrogenesis in the presence or absence of PAI-1, SorlA is required for PAI-1 to promote scarring. These results, together with data showing increased SorlA levels in human IPF lung tissue, support a novel mechanism through which the potent profibrotic mediator PAI-1 drives lung fibrosis and implicate SorlA as a new therapeutic target in IPF treatment.

pathology↗