Different Isoforms of the Neuronal Guidance Molecule Slit2 Directly Cause Chemoattraction or Chemorepulsion of Human Neutrophils

Abstract

The movement of neutrophils between blood and tissues appears to be regulated by chemoattractants and chemorepellents. Compared to neutrophil chemoattractants, relatively little is known about neutrophil chemorepellents. Slit proteins are endogenously cleaved into a variety of N and C terminal fragments, and these fragments are neuronal chemorepellents and inhibit chemoattraction of many cell types, including neutrophils. In this report, we show that the 140 kDa N-terminal Slit2 fragment (Slit2-N) is a chemoattractant and the 110 kDa N-terminal Slit2 fragment (Slit2-S) is a chemorepellent for human neutrophils. The effects of both Slit2 fragments were blocked by antibodies to the Slit2 receptor Robo1 or the Slit2 co-receptor syndecan-4. Slit2-N did not appear to activate Ras, but increased PIP3 levels. Slit2-N induced chemoattraction was unaffected by Ras inhibitors, reversed by PI3 kinase inhibitors, and blocked by cdc42 and Rac inhibitors. In contrast, Slit2-S activated Ras but did not increase PIP3 levels. Slit2-S induced chemorepulsion was blocked by Ras and Rac inhibitors, not affected by PI3 kinase inhibitors, and was reversed by cdc42 inhibitors. Slit2-N but not Slit2-S increased neutrophil adhesion, myosin II light chain phosphorylation, and polarized actin formation and single pseudopods at the leading edge of cells. Slit2-S induced multiple pseudopods. These data suggest that Slit-2 isoforms use similar receptors but different intracellular signaling pathways, and have different effects on the cytoskeleton and pseudopods, to induce neutrophil chemoattraction or chemorepulsion.

SLIT2 Overexpression in Periodontitis Intensifies Inflammation and Alveolar Bone Loss, Possibly via the Activation of MAPK Pathway

“…In this study, SLIT2 increased the MVD and leucocyte/macrophage infiltration in PAPT. Pilling et al (2019) recently reported the SLIT2 isoform-specific neutrophil chemorepellent and chemoattractant functions. The ∼140-kDa N-terminal Slit2 fragment (Slit2-N) enhances, and the ∼110-kDa N-terminal Slit2 fragment (Slit2-S) inhibits neutrophil migration via binding with same ROBO1 receptor.…”

The Role of the Slit/Robo Signaling Pathway

“…On the contrary, a recent paper suggested that Slit2 can also cause chemorepulsion of human neutrophils other than chemoattraction 95. In their report, the authors showed that Slit2 comprises ∼140-kDa N-terminal Slit2 fragment (Slit2-N), which serves as a chemoattractant for human neutrophils, and ∼110-kDa N-terminal Slit2 fragment (Slit2-S), which serves as a chemorepellent for human neutrophis 95. They further found that the effects of both Slit2 fragments were blocked by Abs to the Slit2 receptor Roundabout homolog 1 or the Slit2 coreceptor Syndecan-4, but involved in different intracellular signaling pathways 95.…”

“…On the contrary, a recent paper suggested that Slit2 can also cause chemorepulsion of human neutrophils other than chemoattraction 95. In their report, the authors showed that Slit2 comprises ∼140-kDa N-terminal Slit2 fragment (Slit2-N), which serves as a chemoattractant for human neutrophils, and ∼110-kDa N-terminal Slit2 fragment (Slit2-S), which serves as a chemorepellent for human neutrophis 95.…”

“…In their report, the authors showed that Slit2 comprises ∼140-kDa N-terminal Slit2 fragment (Slit2-N), which serves as a chemoattractant for human neutrophils, and ∼110-kDa N-terminal Slit2 fragment (Slit2-S), which serves as a chemorepellent for human neutrophis 95. They further found that the effects of both Slit2 fragments were blocked by Abs to the Slit2 receptor Roundabout homolog 1 or the Slit2 coreceptor Syndecan-4, but involved in different intracellular signaling pathways 95. These evidences remind of us that numerous works are needed to determining the clear role of Slit/Robo in leukocyte regulation.…”

Axon Guidance Molecules Guiding Neuroinflammation

“…One interesting property of the Slit ligands is that they can interact with different receptors by undergoing proteolytic processing [57]. For example, Slit2 is cleaved into N-terminal and C-terminal fragments, which differentially regulate the chemotactic behaviors of neutrophils via attractive and repulsive effects, respectively [58]. In the nervous system, the N-terminal Slit2 fragment interacts with APPs [59], the precursor of the beta-amyloid peptide which contributes to Alzheimer's disease.…”