"We have identified a target antigen in autoimmune cerebellar degeneration, beta-NAP, that is closely related to the beta-adaptin and beta-COP coat proteins."

"Beta-NAP is a nonclathrin-associated phosphoprotein expressed exclusively in neurons, from E12 through adulthood."

"Beta-NAP is present in the neuronal soma and nerve terminal as soluble and membrane-bound pools"

"and is associated with a discrete set of nerve-terminal vesicles"

"We propose a model in which beta-NAP mediates vesicle transport between the soma and the axon terminus"

"In vitro binding assays showed that mammalian AP-3 did associate with clathrin by interaction of the appendage domain of its beta3 subunit with the amino-terminal domain of the clathrin heavy chain."

"by interaction of the appendage domain of its beta3 subunit with the amino-terminal domain of the clathrin heavy chain"

"AP-3 colocalized with clathrin in cells as observed by immunofluorescence and immunoelectron microscopy."

"Thus, AP-3 function in protein sorting may depend on clathrin."

"However, only beta3A, beta3B, and the point mutant gave full functional rescue, as assayed by LAMP-1 sorting."

"These results indicate that the hinge and/or ear domains of beta3 are important for function, but the clathrin binding site is not needed."

"this construct, like the others, was at least partially localized to structures that were negative for clathrin."

"Finally, binding of the second Arf1 molecule provides the template for AP-3 dimerization, providing a glimpse into the first step of coat polymerization."

"We propose coat polymerization only occurs after cargo engagement, thereby linking cargo sorting with assembly of higher-order coat structures."

"While it is still unknown whether AP-3 can form tubular coats akin to AP-1, our findings that AP-3 contains multiple AH domains and can co-opt Arf1 for homodimerization suggests that a clathrin-independent tubular coat for AP-3 is likely."

"By demonstrating that AP3:ARF1 can generate carriers without using a clathrin lattice, we explain the clathrin independence of AP3-mediated trafficking."

"Targeted point mutations disrupting critical AP3:ARF1 and AP3:AP3 lattice interfaces disrupt AP3 recruitment, carrier formation, and lysosomal cargo trafficking in cells."

"Neurons express adaptor (AP)-3 complexes assembled with either ubiquitous (beta3A) or neuronal-specific (beta3B) beta3 isoforms."

"At the cellular level, AP-3 isoforms were localized to distinct neuronal domains. beta3B-containing AP-3 complexes were preferentially targeted to neuronal processes."

"Consistently, beta3B deficiency compromised synaptic zinc stores assessed by Timm's staining and the synaptic vesicle targeting of membrane proteins involved in zinc uptake (ZnT3 and ClC-3)."

"These observations indicate that the functions of beta3A- and beta3B-containing complexes are distinct and divergent."

"Our results suggest that concerted nonredundant functions of neuronal and ubiquitous AP-3 provide a mechanism to control the levels of selected membrane proteins in synaptic vesicles."

"endogenous Rab32 and Rab38 were found to interact with BLOC-2, AP-1 and AP-3 in membrane, but not cytosolic fractions"

"The localization of Rab32 and Rab38 is likely to specific tubular domains of early/recycling endosomes that contain AP-1, AP-3 or BLOC-2."

"Packaging of the tyrosinases into transport vesicles at early/recycling endosome-associated tubules is dependent on ubiquitous adaptor protein complex (AP)-1 and AP-3"

"AP3B2 encodes the beta-2 subunit of the adaptor-related protein complex 3 (AP-3)"

"AP-3 plays a role in protein sorting in the late-Golgi/trans-Golgi network (TGN) and/or endosomes"

"Biallelic loss-of-function mutations in AP3B2 cause developmental and epileptic encephalopathy 48 (DEE48)"

"The study demonstrated that in mouse hippocampal neurons and slices, AP-3 generates a subset of synaptic vesicles that respond specifically to high-frequency stimulation. Proteomics analysis identified the phospholipid flippase ATP8A1 and its auxiliary subunit TMEM30A as AP-3-dependent synaptic vesicle cargoes."

"First, AP-3 confers axonal polarity of dopamine release by targeting vesicular monoamine transporter 2 (VMAT2) to axons rather than dendrites. Second, AP-3 acting locally at nerve terminals produces synaptic vesicles that respond specifically to high-frequency stimulation."

"This work revealed that dimerization of AP-3 is mediated by the small GTPase Arf1, using the same interface that mediates Arf polymerization... Three distinct structural states were identified: AP-3 bound to a single Arf1 on the delta subunit, AP-3 bound to two Arf1 copies with LAMP1 cargo, and a dimer of the double-Arf1-cargo-AP-3 complex."

"Vesicles derived via the AP-3-dependent recycling pathway contribute specifically to asynchronous release and influence information transfer."

"Loss of the ubiquitous isoform (beta3A) has the opposite effect, significantly increasing synaptic zinc and zinc transporter content."

"The evidence supports a model where **AP-3 is primarily an Arf1-dependent cargo adaptor/coat complex** rather than a clathrin adaptor."

"Clathrin binding is biochemically real but functionally dispensable for core AP-3 sorting (Peden et al. 2002). Should not be the primary MF annotation."

"**AP3B2 clathrin-binding dispensability not directly tested.**"