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Journal of Neuroinflammation

, 9:261

First Online: 29 November 2012Received: 07 September 2012Accepted: 09 November 2012


BackgroundHuman Immunodeficiency Virus-1 HIV-1 associated neurocognitive disorders HANDs are accompanied by significant morbidity, which persists despite the use of combined antiretroviral therapy cART. While activated microglia play a role in pathogenesis, changes in their immune effector functions, including phagocytosis and proinflammatory signaling pathways, are not well understood. We have identified leucine-rich repeat kinase 2 LRRK2 as a novel regulator of microglial phagocytosis and activation in an in vitro model of HANDs, and hypothesize that LRRK2 kinase inhibition will attenuate microglial activation during HANDs.

MethodsWe treated BV-2 immortalized mouse microglia cells with the HIV-1 trans activator of transcription Tat protein in the absence or presence of LRRK2 kinase inhibitor LRRK2i. We used Western blot, qRT-PCR, immunocytochemistry and latex bead engulfment assays to analyze LRRK2 protein levels, proinflammatory cytokine and phagocytosis receptor expression, LRRK2 cellular distribution and phagocytosis, respectively. Finally, we utilized ex vivo microfluidic chambers containing primary hippocampal neurons and BV-2 microglia cells to investigate microglial phagocytosis of neuronal axons.

ResultsWe found that Tat-treatment of BV-2 cells induced kinase activity associated phosphorylation of serine 935 on LRRK2 and caused the formation of cytoplasmic LRRK2 inclusions. LRRK2i decreased Tat-induced phosphorylation of serine 935 on LRRK2 and inhibited the formation of Tat-induced cytoplasmic LRRK2 inclusions. LRRK2i also decreased Tat-induced process extension in BV-2 cells. Furthermore, LRRK2i attenuated Tat-induced cytokine expression and latex bead engulfment. We examined relevant cellular targets in microfluidic chambers and found that Tat-treated BV-2 microglia cells cleared axonal arbor and engulfed neuronal elements, whereas saline treated controls did not. LRRK2i was found to protect axons in the presence of Tat-activated microglia, as well as AnnexinV, a phosphatidylserine-binding protein. In addition, LRRK2i decreased brain-specific angiogenesis inhibitor 1 BAI1 receptor expression on BV-2 cells after Tat-treatment, a key receptor in phosphatidylserine-mediated phagocytosis.

ConclusionTaken together, these results implicate LRRK2 as a key player in microglial inflammation and, in particular, in the phagocytosis of neuronal elements. These studies show that LRRK2 kinase inhibition may prove an effective therapeutic strategy for HANDs, as well as other neuroinflammatory conditions.

KeywordsPhagocytosis Microglia HIV-1 Tat Leucine-rich repeat kinase 2 LRRK2 AnnexinV Parkinson’s disease Brain-specific angiogenesis inhibitor 1 BAI1 AbbreviationsAβAmyloid β

BSABovine serum albumin

cARTCombination antiretroviral therapy

CNSCentral nervous system

DMEMDulbecco’s modified Eagle’s serum

ECLEnhanced chemiluminescence

FBSFetal bovine serum

HANDSHIV-1 associated neurocognitive disorders




LRRK2Leucine-rich repeat kinase 2

LRRK2iLeucine-rich repeat kinase 2 inhibitor

MAPKKKMitogen-activated protein kinase kinase kinase

NF-κβNuclear factor-kappa beta

PBSPhosphate-buffered serum

PDParkinson’s disease

pS935Phosphorylation of serine 935

PVDFPolyvinylidene difluoride

qRT-PCRQuantitative reverse transcriptase-polymerase chain reaction

TatTrans activator of transcription

TNF-αTumor necrosis factor α.

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Autor: Daniel F Marker - Jenna M Puccini - Taryn E Mockus - Justin Barbieri - Shao-Ming Lu - Harris A Gelbard


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