Shaw, Gerry

Coronin‐1a is an evolutionarily conserved protein involved in rearrangements of the actin cytoskeleton. The expression of coronin‐1a is restricted to cells of the hematopoietic lineage. Microglia are resident immune cells of the central nervous system thought to have hematopoietic origins. The aim of this study was to determine if coronin‐1a could be used as a marker for detecting microglia in mammalian species. Using a polyclonal antibody and immunohistochemistry, we show that coronin‐1a is an effective marker for microglia in tissue culture and archival formalin fixed, paraffin embedded tissue, including a range of neurodegenerative and neuroinflammatory conditions and transgenic mice. In human, monkey, horse, rat and mouse tissue coronin‐1a immunoreactivity was present in cells with the morphology and distribution of microglia, even in sections that had been stored for long periods of time. The identity of coronin‐1a positive cells as microglia was confirmed with double immunolabeling for HLA‐DR and Iba‐1. Coronin‐1a immunoreactivity was also detected in T‐ and B‐lymphocytes in lymphoid tissue and neuroinflammatory conditions, but it was not expressed by astrocytes or oligodendrocytes. The results demonstrate that coronin‐1a is a novel marker for microglia in routinely processed tissue from normal and neurodegenerative conditions in both humans and animals.

Hyperphosphorylation and aggregation of tau are observed in multiple neurodegenerative diseases termed tauopathies. Tau has also been implicated in the pathogenesis of Parkinson's disease (PD) and parkinsonisms. Some PD patients with mutations in the leucine‐rich repeat kinase 2 (LRRK2) gene exhibit tau pathology. Mutations in LRRK2 are a major risk factor for PD, but LRRK2 protein function remains unclear. The most common mutation, G2019S, is located in the kinase domain of LRRK2 and enhances kinase activity in vitro. This suggests that the kinase activity of LRRK2 may underlie its cellular toxicity. Recently, in vitro studies have suggested a direct interaction between tubulin‐bound tau and LRRK2 that results in tau phosphorylation at one identified site. Here we present data suggesting that microtubules (MTs) enhance LRRK2‐mediated tau phosphorylation at three different epitopes. We also explore the effect of divalent cations as catalytic cofactors for G2019S LRRK2‐mediated tau phosphorylation and show that manganese does not support kinase activity but inhibits the efficient ability of magnesium to catalyze LRRK2‐mediated phosphorylation of tau. These results suggest that cofactors such as MTs and cations in the cellular milieu have an important impact on LRRK2‐tau interactions and resultant tau phosphorylation. © 2015 Wiley Periodicals, Inc.

This study identifies the actin-binding protein, coronin-1a, as a novel and effective immunohistochemical marker for microglia in both cell cultures and in formaldehyde-fixed, paraffin-embedded tissue. Antibodies to coronin-1a effectively immunostained microglia in human, monkey, horse, rat, and mouse tissues, even in tissues stored for long periods of time. The identity of coronin-1a-immunoreactive cells as microglia was confirmed using double immunolabeling with cell type-specific markers as well as by morphological features and the distribution of immunoreactive cells. These properties are shared by another actin-binding protein, IBA-1. Unlike IBA-1, coronin-1a immunoreactivity was also detected in lymphocytes and certain other hematopoietic cells. The results indicate that both coronin-1a and IBA-1 are robust markers for microglia that can be used in routinely processed tissue of humans and animals. Because both coronin-1a and IBA-1 are actin-binding proteins that play a role in rearrangement of the membrane cytoskeleton, it suggests that these proteins are critical to dynamic properties of microglia.