Human immunodeficiency virus-1 Tat activates calpain proteases via the ryanodine receptor to enhance surface dopamine transporter levels and increase transporter-specific uptake and Vmax.
Human immunodeficiency virus-associated neurological disease (HAND) still causes significant morbidity, despite success reducing viral loads with combination antiretroviral therapy. The dopamine (DA) system is particularly vulnerable in HAND. We hypothesize that early, "reversible" DAergic synaptic dysfunction occurs long before DAergic neuron loss. As such, aging human immunodeficiency virus (HIV)-infected individuals may be vulnerable to other age-related neurodegenerative diseases like Parkinson's disease (PD), underscoring the need to understand shared molecular targets in HAND and PD. Previously, we reported that the neurotoxic HIV-1 transactivating factor (Tat) acutely disrupts mitochondrial and endoplasmic reticulum calcium homeostasis via ryanodine receptor (RyR) activation. Here, we further report that Tat disrupts DA transporter (DAT) activity and function, resulting in increased plasma membrane (PM) DAT and increased DAT V(max), without changes in K(m) or total DAT protein. Tat also increases calpain protease activity at the PM, demonstrated by total internal reflection fluorescence microscopy of a cleavable fluorescent calpain substrate. Tat-increased PM DAT and calpain activity are blocked by the RyR antagonists ryanodine and dantrolene, the calpain inhibitor calpastatin, and by a specific inhibitor of GSK-3β. We conclude that Tat activates RyRs via a calcium- and calpain-mediated mechanism that upregulates DAT trafficking to the PM, and is independent of DAT protein synthesis, reinforcing the feasibility of RyR and GSK-3β inhibition as clinical therapeutic approaches for HAND. Finally, we provide key translational relevance for these findings by highlighting published human data of increased DAT levels in striata of HAND patients and by demonstrating similar findings in Tat-expressing transgenic mice.
Center for Neural Development and Disease, Department of Neurology, Child Neurology Division, Graduate Program in Pathology, and Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA. seth_perry@urmc.rochester.edu
Seth W
SW
Perry
Justin
J
Barbieri
Ning
N
Tong
Oksana
O
Polesskaya
Santosh
S
Pudasaini
Angela
A
Stout
Rebecca
R
Lu
Michelle
M
Kiebala
Sanjay B
SB
Maggirwar
Harris A
HA
Gelbard
D015526:AIDS Dementia Complex / Q000201:enzymology / Q000473:pathology; D000818:Animals; D015153:Blotting, Western; D002154:Calpain / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D007700:Kinetics; D008636:Mesencephalon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000378:metabolism; D016716:PC12 Cells; D010447:Peptide Hydrolases / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects*; D013347:Subcellular Fractions / Q000502:physiology; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000494:pharmacology*
D050483:Dopamine Plasma Membrane Transport Proteins; D011480:Protease Inhibitors; D019837:Ryanodine Receptor Calcium Release Channel; D054322:tat Gene Products, Human Immunodeficiency Virus; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D010447:Peptide Hydrolases; D002154:Calpain