Analysis of protein trafficking between mitochondria and the endoplasmic reticulum by fluorescence microscopy.

Precise protein localization is essential for normal cellular functions. However, recent studies have revealed that protein targeting is error-prone, and tail-anchored proteins mistargeted to mitochondria are transferred to the endoplasmic reticulum (ER) by an ATPase Msp1 (yeast)/ATAD1 (human) in the mitochondrial outer membrane for further quality examination in the ER to determine their fate, degradation or re-targeting. Analysis of the inter-organelle transfer of proteins requires a combination of time-lapse fluorescence microscopy and a system to achieve regulation of the protein levels of both transfer substrates and factors regulating the transfer in a coordinated manner at precise timing.

Central nervous system specific high molecular weight ALS2/alsin homophilic complex is enriched in mouse brain synaptosomes.

ALS2/alsin, the causative gene product for a number of juvenile recessive motor neuron diseases, acts as a guanine nucleotide exchange factor (GEF) for Rab5, regulating early endosome trafficking and maturation. It has been demonstrated that ALS2 forms a tetramer, and this oligomerization is essential for its GEF activity and endosomal localization in established cancer cells. However, despite that ALS2 deficiency is implicated in neurological diseases, neither the subcellular distribution of ALS2 nor the form of its complex in the central nervous system (CNS) has been investigated.

GET pathway mediates transfer of mislocalized tail-anchored proteins from mitochondria to the ER.

Tail-anchored (TA) membrane proteins have a potential risk to be mistargeted to the mitochondrial outer membrane (OM). Such mislocalized TA proteins can be extracted by the mitochondrial AAA-ATPase Msp1 from the OM and transferred to the ER for ER protein quality control involving ubiquitination by the ER-resident Doa10 complex. Yet it remains unclear how the extracted TA proteins can move to the ER crossing the aqueous cytosol and whether this transfer to the ER is essential for the clearance of mislocalized TA proteins.

High-throughput quantitative analysis of axonal transport in cultured neurons from SOD1 ALS mice by using a microfluidic device.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by selective loss of motor neurons. We have previously shown that autophagosome-like vesicular structures are progressively accumulated in the spinal axons of an ALS mouse model, overexpressing human Cu/Zn superoxide dismutase (SOD1) mutant, prior to the onset of motor symptoms. This suggests that axonal transport perturbation can be an early sign of neuronal dysfunction.

The N-terminal intrinsically disordered region mediates intracellular localization and self-oligomerization of ALS2.

ALS2, a product of the causative gene for familial amyotrophic lateral sclerosis (ALS) type 2, plays a pivotal role in the regulation of endosome dynamics by activating small GTPase Rab5 via its intrinsic guanine nucleotide-exchange factor activity. Previously, we have reported that the N-terminal region of ALS2 has crucial roles in its endosomal localization and self-oligomerization, both of which are indispensable for the cellular function of ALS2. The N-terminus of ALS2 contains the regulator of chromosome condensation 1-like domain (RLD), which is predicted to form a seven-bladed β-propeller structure.

SQSTM1 variant that is linked to sporadic ALS exhibits impaired association with MAP1LC3 in cultured cells.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are genetically, pathologically and clinically-related progressive neurodegenerative diseases. Thus far, several variations have been identified in patients with ALS and FTD. However, it remains unclear how variations lead to neurodegeneration.

ALS2, the small GTPase Rab17-interacting protein, regulates maturation and sorting of Rab17-associated endosomes.

Small GTPase Rab17 has been shown to regulate a wide range of physiological processes including cell migration in tumor cells and dendrite morphogenesis in neurons. However, molecular mechanism underlying Rab17-mediated intracellular trafficking is still unclear. To address this issue, we focused on Rab17-interacting protein ALS2, which was also known as a guanine nucleotide exchange factor (GEF) for Rab5, and investigated how ALS2 contributed to Rab17-associated membrane trafficking in cells.

Altered oligomeric states in pathogenic ALS2 variants associated with juvenile motor neuron diseases cause loss of ALS2-mediated endosomal function.

Familial amyotrophic lateral sclerosis type 2 (ALS2) is a juvenile autosomal recessive motor neuron disease caused by the mutations in the gene. The gene product, ALS2/alsin, forms a homophilic oligomer and acts as a guanine nucleotide-exchange factor (GEF) for the small GTPase Rab5. This oligomerization is crucial for both Rab5 activation and ALS2-mediated endosome fusion and maturation in cells.

Systemic overexpression of SQSTM1/p62 accelerates disease onset in a SOD1-expressing ALS mouse model.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by a selective loss of upper and lower motor neurons. Recent studies have shown that mutations in SQSTM1 are linked to ALS. SQSTM1 encodes SQSTM1/p62 that regulates not only autophagy via the association with MAP1LC3/LC3 and ubiquitinated proteins but also the KEAP1-NFE2L2/Nrf2 anti-oxidative stress pathway by interacting with KEAP1.

Functional links between SQSTM1 and ALS2 in the pathogenesis of ALS: cumulative impact on the protection against mutant SOD1-mediated motor dysfunction in mice.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by a selective loss of motor neurons in the brain and spinal cord. Multiple toxicity pathways, such as oxidative stress, misfolded protein accumulation, and dysfunctional autophagy, are implicated in the pathogenesis of ALS. However, the molecular basis of the interplay between such multiple factors in vivo remains unclear.