Leucine-rich repeat kinase 2 regulates autophagy through a calcium-dependent pathway involving NAADP

Abstract

Mutations in the leucine-rich repeat kinase-2 (LRRK2) gene cause late-onset Parkinson’s disease, but its physiological function has remained largely unknown. Here we report that LRRK2 activates a calcium-dependent protein kinase kinase-β (CaMKK-β)/adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway which is followed by a persistent increase in autophagosome formation. Simultaneously, LRKR2 overexpression increases the levels of the autophagy receptor p62 in a protein synthesis-dependent manner, and decreases the number of acidic lysosomes. The LRRK2-mediated effects result in increased sensitivity of cells to stressors associated with abnormal protein degradation. These effects can be mimicked by the lysosomal Ca2+-mobilizing messenger nicotinic acid adenine dinucleotide phosphate (NAADP) and can be reverted by an NAADP receptor antagonist or expression of dominant-negative receptor constructs. Collectively, our data indicate a molecular mechanism for LRRK2 deregulation of autophagy and reveal previously unidentified therapeutic targets.

Lewy Body-like α-Synuclein Aggregates Resist Degradation and Impair Macroautophagy

“…Therefore, impairment of autophagy may lead to cell death through several different mechanisms, including oxidative stress, which is strongly implicated in PD pathogenesis (71,72). Indeed, several proteins that are implicated in PD pathogenesis, including ATP13A2, LRRK2 and Pink-1, may also affect autophagy function (73)(74)(75), suggesting that autophagic dysfunction may be a primary cause of cell death in PD.…”

Cellular processes associated with LRRK2 function and dysfunction

“…Overexpression of G2019S or WT‐LRRK2 was able to reduce the payload of chaperone‐mediated autophagy, indicating that an accumulation of α‐synuclein, and misfolded proteins in general, as seen in PD, may be a partial consequence of a LRRK2‐mediated alteration of cellular proteolytic pathways 108. LRRK2 kinase inhibitors and knockdown 109, 110, 111, as well as LRRK2 overexpression in cell models 80, were able to modify the macroautophagic flux in vitro ; however, it is still debatable whether LRRK2 possesses a positive or negative regulatory role in the control of macroautophagy and if the role of LRRK2 resides within the initiation or the clearance steps. This open debate has been further emphasized by the study of LRRK2 knockout animal models.…”

Two-pore channels (TPCs): Novel voltage-gated ion channels with pleiotropic functions

“…During cell starvation, ATP levels fall, mTOR delocalizes from TPCs, and the channel opens. 6,15,38 As well, due to the fact that TPCs are involved in the regulation of multiple biological functions, different protein kinasas have been suggested to regulate TPCs activity: the leucine-rich repeat kinase 2 (LRRK2) has been proposed to regulate autophagy through TPC2 activation 13 while JNK and P38 kinases have shown to inhibit TPC2 NAADP-mediated Ca 2C release. 15 Finally, it has been recently demonstrated that TPC1 function is dependent of a COOH-terminal helix that allow channel dimerization and, consequently, its function.…”

“…4 Still, on the other hand, in 2012 and 2013 2 independent studies refuted that mammalian TPCs were Ca 2C release channels activated by NAADP, probing that they are not Ca 2C but Na C release channels that are not activated by NAADP but by phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) and inhibited by the mammalian target of rapamycin (mTOR), 5,6 which caused a great commotion regarding TPCs regulation and function among the scientific community. [7][8][9][10] Nowadays, it is accepted that mammalian TPCs not only function as Ca 2C or Na C release channels, but also as H C and K C channels, 11,12 and it has been demonstrated that TPCs can be activated by other signals apart from NAADP and PI (3,5)P2, such as the leucine-rich repeat kinase 2 (LRRK2) 13 or action potentials, 14 and inhibited by Mg 2C concentrations, 15 Ca 2C and Na C ion channels inhibitors, 16,17 or c-Jun N-terminal kinase (JNK) and p38 kinase, 15 apart from mTOR. So that, it seems reasonable that, according to the cellular context, TPCs could be differentially regulated and exert different functions.…”