The open architecture of HD-PTP phosphatase provides new insights into the mechanism of regulation of ESCRT function

Ptpn23 Controls Cardiac T-Tubule Patterning by Promoting the Assembly of Dystrophin-Glycoprotein Complex

BACKGROUND

Cardiac transverse tubules (T-tubules) are anchored to sarcomeric Z-discs by costameres to establish a regular spaced pattern. One of the major components of costameres is the dystrophin-glycoprotein complex (DGC). Nevertheless, how the assembly of the DGC coordinates with the formation and maintenance of T-tubules under physiological and pathological conditions remains unclear.

METHODS

Given the known role of Ptpn23 (protein tyrosine phosphatase, nonreceptor type 23) in regulating membrane deformation, its expression in patients with dilated cardiomyopathy was determined. Taking advantage of Cre/Loxp, CRISPR/Cas9, and adeno-associated virus 9 (AAV9)-mediated in vivo gene editing, we generated cardiomyocyte-specific Ptpn23 and Actn2 (α-actinin-2, a major component of Z-discs) knockout mice. We also perturbed the DGC by using dystrophin global knockout mice (DmdE4*). MM 4-64 and Di-8-ANEPPS staining, Cav3 immunofluorescence, and transmission electron microscopy were performed to determine T-tubule structure in isolated cells and intact hearts. In addition, the assembly of the DGC with Ptpn23 and dystrophin loss of function was determined by glycerol-gradient fractionation and SDS-PAGE analysis.

RESULTS

The expression level of Ptpn23 was reduced in failing hearts from dilated cardiomyopathy patients and mice. Genetic deletion of Ptpn23 resulted in disorganized T-tubules with enlarged diameters and progressive dilated cardiomyopathy without affecting sarcomere organization. AAV9-mediated mosaic somatic mutagenesis further indicated a cell-autonomous role of Ptpn23 in regulating T-tubule formation. Genetic and biochemical analyses showed that Ptpn23 was essential for the integrity of costameres, which anchor the T-tubule membrane to Z-discs, through interactions with α-actinin and dystrophin. Deletion of α-actinin altered the subcellular localization of Ptpn23 and DGCs. In addition, genetic inactivation of dystrophin caused similar T-tubule defects to Ptpn23 loss-of-function without affecting Ptpn23 localization at Z-discs. Last, inducible Ptpn23 knockout at 1 month of age showed Ptpn23 is also required for the maintenance of T-tubules in adult cardiomyocytes.

CONCLUSIONS

Ptpn23 is essential for cardiac T-tubule formation and maintenance along Z-discs. During postnatal heart development, Ptpn23 interacts with sarcomeric α-actinin and coordinates the assembly of the DGC at costameres to sculpt T-tubule spatial patterning and morphology.

Cell entry and release of quasi-enveloped human hepatitis viruses

Infectious hepatitis type A and type E are caused by phylogenetically distinct single-stranded, positive-sense RNA viruses that were once considered to be non-enveloped. However, studies show that both are released nonlytically from hepatocytes as 'quasi-enveloped' virions cloaked in host membranes. These virion types predominate in the blood of infected individuals and mediate virus spread within the liver. They lack virally encoded proteins on their surface and are resistant to neutralizing anti-capsid antibodies induced by infection, yet they efficiently enter cells and initiate new rounds of virus replication. In this Review, we discuss the mechanisms by which specific peptide sequences in the capsids of these quasi-enveloped virions mediate their endosomal sorting complexes required for transport (ESCRT)-dependent release from hepatocytes through multivesicular endosomes, what is known about how they enter cells, and the impact of capsid quasi-envelopment on host immunity and pathogenesis.

Genetic Variants in Protein Tyrosine Phosphatase Non-Receptor Type 23 Are Responsible for Mesiodens Formation

A mesiodens is a supernumerary tooth located in the midline of the premaxilla. To investigate the genetic cause of mesiodens, clinical and radiographic examination were performed on 23 family members of a two-generation Hmong family. Whole exome sequencing (WES) or Sanger sequencing were performed in 22 family members and two unrelated Thai patients with mesiodens. WES in the Hmong family revealed a missense mutation (c.1807G>A;p.Glu603Lys) in PTPN23 in seven affected members and six unaffected members. The mode of inheritance was autosomal dominance with incomplete penetrance (53.84%). Two additional mutations in PTPN23, c.2248C>G;p.Pro750Ala and c.3298C>T;p.Arg1100Cys were identified in two unrelated patients with mesiodens. PTPN23 is a regulator of endosomal trafficking functioning to move activated membrane receptors, such as EGFR, from the endosomal sorting complex towards the ESCRT-III complex for multivesicular body biogenesis, lysosomal degradation, and subsequent downregulation of receptor signaling. Immunohistochemical study and RNAscope on developing mouse embryos showed broad expression of PTPN23 in oral tissues, while immunofluorescence showed that EGFR was specifically concentrated in the midline epithelium. Importantly, PTPN23 mutant protein was shown to have reduced phosphatase activity. In conclusion, mesiodens were associated with genetic variants in PTPN23, suggesting that mesiodens may form due to defects in endosomal trafficking, leading to disrupted midline signaling.

Overcoming the blood-brain barrier: Exosomes as theranostic nanocarriers for precision neuroimaging

Exosomes are cell-derived vesicles with a lipid bilayer membrane that play important roles in intercellular communication. They provide an unprecedented opportunity for the development of drug delivery nanoplatforms due to their low immunogenicity, low toxicity, biocompatibility, stability, and ability to change the functions of recipient cells. In addition, exosomes can penetrate the blood-brain barrier and then target and accumulate in relevant pathological brain regions. However, few studies have focused on the applications of exosomes as nanocarriers for use in precision neuroimaging studies. Thus, this report presents the feasibility of fabricating specific exosome-based diagnostic reagents for the application of personalized/precision radiology in the central nervous system based on important recent fundamental discoveries and technological advances.

Nonlytic cellular release of hepatitis A virus requires dual capsid recruitment of the ESCRT-associated Bro1 domain proteins HD-PTP and ALIX

Although picornaviruses are conventionally considered 'nonenveloped', members of multiple picornaviral genera are released nonlytically from infected cells in extracellular vesicles. The mechanisms underlying this process are poorly understood. Here, we describe interactions of the hepatitis A virus (HAV) capsid with components of host endosomal sorting complexes required for transport (ESCRT) that play an essential role in release. We show release of quasi-enveloped virus (eHAV) in exosome-like vesicles requires a conserved export signal located within the 8 kDa C-terminal VP1 pX extension that functions in a manner analogous to late domains of canonical enveloped viruses. Fusing pX to a self-assembling engineered protein nanocage (EPN-pX) resulted in its ESCRT-dependent release in extracellular vesicles. Mutational analysis identified a 24 amino acid peptide sequence located within the center of pX that was both necessary and sufficient for nanocage release. Deleting a YxxL motif within this sequence ablated eHAV release, resulting in virus accumulating intracellularly. The pX export signal is conserved in non-human hepatoviruses from a wide range of mammalian species, and functional in pX sequences from bat hepatoviruses when fused to the nanocage protein, suggesting these viruses are released as quasi-enveloped virions. Quantitative proteomics identified multiple ESCRT-related proteins associating with EPN-pX, including ALG2-interacting protein X (ALIX), and its paralog, tyrosine-protein phosphatase non-receptor type 23 (HD-PTP), a second Bro1 domain protein linked to sorting of ubiquitylated cargo into multivesicular endosomes. RNAi-mediated depletion of either Bro1 domain protein impeded eHAV release. Super-resolution fluorescence microscopy demonstrated colocalization of viral capsids with endogenous ALIX and HD-PTP. Co-immunoprecipitation assays using biotin-tagged peptides and recombinant proteins revealed pX interacts directly through the export signal with N-terminal Bro1 domains of both HD-PTP and ALIX. Our study identifies an exceptionally potent viral export signal mediating extracellular release of virus-sized protein assemblies and shows release requires non-redundant activities of both HD-PTP and ALIX.

Pseudophosphatases as Regulators of MAPK Signaling

Mitogen-activated protein kinase (MAPK) signaling pathways are highly conserved regulators of eukaryotic cell function. These enzymes regulate many biological processes, including the cell cycle, apoptosis, differentiation, protein biosynthesis, and oncogenesis; therefore, tight control of the activity of MAPK is critical. Kinases and phosphatases are well established as MAPK activators and inhibitors, respectively. Kinases phosphorylate MAPKs, initiating and controlling the amplitude of the activation. In contrast, MAPK phosphatases (MKPs) dephosphorylate MAPKs, downregulating and controlling the duration of the signal. In addition, within the past decade, pseudoenzymes of these two families, pseudokinases and pseudophosphatases, have emerged as bona fide signaling regulators. This review discusses the role of pseudophosphatases in MAPK signaling, highlighting the function of phosphoserine/threonine/tyrosine-interacting protein (STYX) and TAK1-binding protein (TAB 1) in regulating MAPKs. Finally, a new paradigm is considered for this well-studied cellular pathway, and signal transduction pathways in general.

Denis N, Gingras AC, Lukacs GL, Pause A. Endofin is required for HD-PTP and ESCRT-0 interdependent endosomal sorting of ubiquitinated transmembrane cargoes

Internalized and ubiquitinated signaling receptors are silenced by their intraluminal budding into multivesicular bodies aided by the endosomal sorting complexes required for transport (ESCRT) machinery. HD-PTP, an ESCRT protein, forms complexes with ESCRT-0, -I and -III proteins, and binds to Endofin, a FYVE-domain protein confined to endosomes with poorly understood roles. Using proximity biotinylation, we showed that Endofin forms a complex with ESCRT constituents and Endofin depletion increased integrin α5-and EGF-receptor plasma membrane density and stability by hampering their lysosomal delivery. This coincided with sustained receptor signaling and increased cell migration. Complementation of Endofin- or HD-PTP-depleted cells with wild-type Endofin or HD-PTP, but not with mutants harboring impaired Endofin/HD-PTP association or cytosolic Endofin, restored EGFR lysosomal delivery. Endofin also promoted Hrs indirect interaction with HD-PTP. Jointly, our results indicate that Endofin is required for HD-PTP and ESCRT-0 interdependent sorting of ubiquitinated transmembrane cargoes to ensure efficient receptor desensitization and lysosomal delivery.

Interactions of ubiquitin and CHMP5 with the V domain of HD-PTP reveals role for regulation of Vps4 ATPase

The family of Bro1 proteins coordinates the activity of the Endosomal Sorting Complexes Required for Transport (ESCRTs) to mediate a number of membrane remodeling events. These events culminate in membrane scission catalyzed by ESCRT-III, whose polymerization and disassembly is controlled by the AAA-ATPase, Vps4. Bro1-family members Alix and HD-PTP as well as yeast Bro1 have central “V” domains that noncovalently bind Ub and connect ubiquitinated proteins to ESCRT-driven functions such as the incorporation of ubiquitinated membrane proteins into intralumenal vesicles of multivesicular bodies. Recently, it was discovered that the V domain of yeast Bro1 binds the MIT domain of Vps4 to stimulate its ATPase activity. Here we determine the structural basis for how the V domain of human HD-PTP binds ubiquitin. The HD-PTP V domain also binds the MIT domain of Vps4, and ubiquitin binding to the HD-PTP V domain enhances its ability to stimulate Vps4 ATPase activity. Additionally, we found that V domains of both HD-PTP and Bro1 bind CHMP5 and Vps60, respectively, providing another potential molecular mechanism to alter Vps4 activity. These data support a model whereby contacts between ubiquitin, ESCRT-III, and Vps4 by V domains of the Bro1 family may coordinate late events in ESCRT-driven membrane remodeling events.

The Roles of Pseudophosphatases in Disease

The pseudophosphatases, atypical members of the protein tyrosine phosphatase family, have emerged as bona fide signaling regulators within the past two decades. Their roles as regulators have led to a renaissance of the pseudophosphatase and pseudoenyme fields, catapulting interest from a mere curiosity to intriguing and relevant proteins to investigate. Pseudophosphatases make up approximately fourteen percent of the phosphatase family, and are conserved throughout evolution. Pseudophosphatases, along with pseudokinases, are important players in physiology and pathophysiology. These atypical members of the protein tyrosine phosphatase and protein tyrosine kinase superfamily, respectively, are rendered catalytically inactive through mutations within their catalytic active signature motif and/or other important domains required for catalysis. This new interest in the pursuit of the relevant functions of these proteins has resulted in an elucidation of their roles in signaling cascades and diseases. There is a rapid accumulation of knowledge of diseases linked to their dysregulation, such as neuropathies and various cancers. This review analyzes the involvement of pseudophosphatases in diseases, highlighting the function of various role(s) of pseudophosphatases involvement in pathologies, and thus providing a platform to strongly consider them as key therapeutic drug targets.

Cell-Secreted Vesicles: Novel Opportunities in Cancer Diagnosis, Monitoring and Treatment

Extracellular vesicles (EVs) are important mediators of intercellular communication playing a pivotal role in the regulation of physiological and pathological processes, including cancer. In particular, there is significant evidence suggesting that tumor-derived EVs exert an immunosuppressive activity during cancer progression, as well as stimulate tumor cell migration, angiogenesis, invasion and metastasis. The use of EVs as a liquid biopsy is currently a fast-growing area of research in medicine, with the potential to provide a step-change in the diagnosis and treatment of cancer, allowing the prediction of both therapy response and prognosis. EVs could be useful not only as biomarkers but also as drug delivery systems, and may represent a target for anticancer therapy. In this review, we attempted to summarize the current knowledge about the techniques used for the isolation of EVs and their roles in cancer biology, as liquid biopsy biomarkers and as therapeutic tools and targets.

Pseudophosphatase MK-STYX: the atypical member of the MAP kinase phosphatases

The regulation of the phosphorylation of mitogen-activated protein kinases (MAPKs) is essential for cellular processes such as proliferation, differentiation, survival, and death. Mutations within the MAPK signaling cascades are implicated in diseases such as cancer, neurodegenerative disorders, arthritis, obesity, and diabetes. MAPK phosphorylation is controlled by an intricate balance between MAPK kinases (enzymes that add phosphate groups) and MAPK phosphatases (MKPs) (enzymes that remove phosphate groups). MKPs are complex negative regulators of the MAPK pathway that control the amplitude and spatiotemporal regulation of MAPKs. MK-STYX (MAPK phosphoserine/threonine/tyrosine-binding protein) is a member of the MKP subfamily, which lacks the critical histidine and nucleophilic cysteine residues in the active site required for catalysis. MK-STYX does not influence the phosphorylation status of MAPK, but even so it adds to the complexity of signal transduction cascades as a signaling regulator. This review highlights the function of MK-STYX, providing insight into MK-STYX as a signal regulating molecule in the stress response, HDAC 6 dynamics, apoptosis, and neurite differentiation.

PTPN23 binds the dynein adaptor BICD1 and is required for endocytic sorting of neurotrophin receptors

Signalling by target-derived neurotrophins is essential for the correct development of the nervous system and its maintenance throughout life. Several aspects concerning the lifecycle of neurotrophins and their receptors have been characterised over the years, including the formation, endocytosis and trafficking of signalling-competent ligand-receptor complexes. However, the molecular mechanisms directing the sorting of activated neurotrophin receptors are still elusive. Previously, our laboratory identified Bicaudal-D1 (BICD1), a dynein motor adaptor, as a key factor for lysosomal degradation of brain-derived neurotrophic factor (BDNF)-activated TrkB (also known as NTRK2) and p75NTR (also known as NGFR) in motor neurons. Here, using a proteomics approach, we identified protein tyrosine phosphatase, non-receptor type 23 (PTPN23), a member of the endosomal sorting complexes required for transport (ESCRT) machinery, in the BICD1 interactome. Molecular mapping revealed that PTPN23 is not a canonical BICD1 cargo; instead, PTPN23 binds the N-terminus of BICD1, which is also essential for the recruitment of cytoplasmic dynein. In line with the BICD1-knockdown phenotype, loss of PTPN23 leads to increased accumulation of BDNF-activated p75NTR and TrkB in swollen vacuole-like compartments, suggesting that neuronal PTPN23 is a novel regulator of the endocytic sorting of neurotrophin receptors.

The ESCRT-II Subunit EAP20/VPS25 and the Bro1 Domain Proteins HD-PTP and BROX Are Individually Dispensable for Herpes Simplex Virus 1 Replication

Capsid envelopment during assembly of the neurotropic herpesviruses herpes simplex virus 1 (HSV-1) and pseudorabies virus (PRV) in the infected cell cytoplasm is thought to involve the late-acting cellular ESCRT (endosomal sorting complex required for transport) components ESCRT-III and VPS4 (vacuolar protein sorting 4). However, HSV-1, unlike members of many other families of enveloped viruses, does not appear to require the ESCRT-I subunit TSG101 or the Bro1 domain-containing protein ALIX (Alg-2-interacting protein X) to recruit and activate ESCRT-III. Alternative cellular factors that are known to be capable of regulating ESCRT-III function include the ESCRT-II complex and other members of the Bro1 family. We therefore used small interfering RNA (siRNA) to knock down the essential ESCRT-II subunit EAP20/VPS25 (ELL-associated protein 20/vacuolar protein sorting 25) and the Bro1 proteins HD-PTP (His domain-containing protein tyrosine phosphatase) and BROX (Bro1 domain and CAAX motif containing). We demonstrated reductions in levels of the targeted proteins by Western blotting and used quantitative microscopic assays to confirm loss of ESCRT-II and HD-PTP function. We found that in single-step replication experiments, the final yields of HSV-1 were unchanged following loss of EAP20, HD-PTP, or BROX.IMPORTANCE HSV-1 is a pathogen of the human nervous system that uses its own virus-encoded proteins and the normal cellular ESCRT machinery to drive the construction of its envelope. How HSV-1 structural proteins interact with ESCRT components and which subsets of cellular ESCRT proteins are utilized by the virus remain largely unknown. Here, we demonstrate that an essential component of the ESCRT-II complex and two ESCRT-associated Bro1 proteins are dispensable for HSV-1 replication.

Shedding Light on Extracellular Vesicle Biogenesis and Bioengineering

Extracellular vesicles (EVs) are biocompatible, nano-sized secreted vesicles containing many types of biomolecules, including proteins, RNAs, DNAs, lipids, and metabolites. Their low immunogenicity and ability to functionally modify recipient cells by transferring diverse bioactive constituents make them an excellent candidate for a next-generation drug delivery system. Here, the recent advances in EV biology and emerging strategies of EV bioengineering are summarized, and the prospects for clinical translation of bioengineered EVs and the challenges to be overcome are discussed.

The many functions of ESCRTs

Cellular membranes can form two principally different involutions, which either exclude or contain cytosol. The 'classical' budding reactions, such as those occurring during endocytosis or formation of exocytic vesicles, involve proteins that assemble on the cytosol-excluding face of the bud neck. Inverse membrane involution occurs in a wide range of cellular processes, supporting cytokinesis, endosome maturation, autophagy, membrane repair and many other processes. Such inverse membrane remodelling is mediated by a heteromultimeric protein machinery known as endosomal sorting complex required for transport (ESCRT). ESCRT proteins assemble on the cytosolic (or nucleoplasmic) face of the neck of the forming involution and cooperate with the ATPase VPS4 to drive membrane scission or sealing. Here, we review similarities and differences of various ESCRT-dependent processes, with special emphasis on mechanisms of ESCRT recruitment.

The endosomal sorting adaptor HD-PTP is required for ephrin-B:EphB signalling in cellular collapse and spinal motor axon guidance

The signalling output of many transmembrane receptors that mediate cell-cell communication is restricted by the endosomal sorting complex required for transport (ESCRT), but the impact of this machinery on Eph tyrosine kinase receptor function is unknown. We identified the ESCRT-associated adaptor protein HD-PTP as part of an EphB2 proximity-dependent biotin identification (BioID) interactome, and confirmed this association using co-immunoprecipitation. HD-PTP loss attenuates the ephrin-B2:EphB2 signalling-induced collapse of cultured cells and axonal growth cones, and results in aberrant guidance of chick spinal motor neuron axons in vivo. HD-PTP depletion abrogates ephrin-B2-induced EphB2 clustering, and EphB2 and Src family kinase activation. HD-PTP loss also accelerates ligand-induced EphB2 degradation, contrasting the effects of HD-PTP loss on the relay of signals from other cell surface receptors. Our results link Eph function to the ESCRT machinery and demonstrate a role for HD-PTP in the earliest steps of ephrin-B:EphB signalling, as well as in obstructing premature receptor depletion.

Deletion of Protein Tyrosine Phosphatase Nonreceptor Type 2 in Intestinal Epithelial Cells Results in Upregulation of the Related Phosphatase Protein Tyrosine Phosphatase Nonreceptor Type 23

Background/Aims

Knockdown of protein tyrosine phosphatase nonreceptor type 2 (PTPN2) exaggerates IFN-γ-induced intestinal barrier defects, but mice constitutively lacking PTPN2 in epithelial cells (PTPN2xVilCre mice) do not show changes in epithelial function or enhanced susceptibility to experimental colitis. Here, we investigated whether PTPN2 modulates the expression of related tyrosine phosphatases.

Methods

PTPN2 knockdown in HT-29 cells was induced using siRNA constructs. Acute colitis in PTPN2xVilCre mice was induced by 2% dextran sulfate sodium (DSS) in drinking water for 7 days. Colitis-associated tumors were induced by injection of azoxymethane prior to treatment with DSS for 3 consecutive cycles.

Results

In HT-29 cells, PTPN2 depletion resulted in enhanced mRNA expression of PTPN11 and PTPN23 and in parallel to upregulation of IL-18 mRNA upon treatment with TNF for 24 h. DSS treatment of PTPN2-deficient mice resulted in a strong induction of Ptpn23 mRNA in colon tissue in vivo. In the tumor model, Ptpn23 mRNA was again clearly upregulated in nontumor tissue from PTPN2-deficient mice; however, this was not observed in tumor tissue.

Conclusions

Our experiments show that PTPN23 function might, at least partially, compensate lack of PTPN2 in epithelial cells. Upregulation of PTPN23 might therefore crucially contribute to the lack of a colitis phenotype in PTPN2-VilCre mice.

Structure and functions of His domain protein tyrosine phosphatase in receptor trafficking and cancer

Cell surface receptors trigger the activation of signaling pathways to regulate key cellular processes, including cell survival and proliferation. Internalization, sorting, and trafficking of activated receptors, therefore, play a major role in the regulation and attenuation of cell signaling. Efficient sorting of endocytosed receptors is performed by the ESCRT machinery, which targets receptors for degradation by the sequential establishment of protein complexes. These events are tightly regulated and malfunction of ESCRT components can lead to abnormal trafficking and sustained signaling and promote tumor formation or progression. In this review, we analyze the modular domain organization of the alternative ESCRT protein HD-PTP and its role in receptor trafficking and tumorigenesis.

Dissecting the role of His domain protein tyrosine phosphatase/PTPN23 and ESCRTs in sorting activated epidermal growth factor receptor to the multivesicular body

Sorting of activated epidermal growth factor receptor (EGFR) into intraluminal vesicles (ILVs) within the multivesicular body (MVB) is an essential step during the down-regulation of the receptor. The machinery that drives EGFR sorting attaches to the cytoplasmic face of the endosome and generates vesicles that bud into the endosome lumen, but somehow escapes encapsulation itself. This machinery is termed the ESCRT (endosomal sorting complexes required for transport) pathway, a series of multi-protein complexes and accessory factors first identified in yeast. Here, we review the yeast ESCRT pathway and describe the corresponding components in mammalian cells that sort EGFR. One of these is His domain protein tyrosine phosphatase (HD-PTP/PTPN23), and we review the interactions involving HD-PTP and ESCRTs. Finally, we describe a working model for how this ESCRT pathway might overcome the intrinsic topographical problem of EGFR sorting to the MVB lumen.

The role of pseudophosphatases as signaling regulators

Pseudophosphatases are atypical members of the protein tyrosine phosphatase superfamily. Mutations within their catalytic signature motif render them catalytically inactive. Despite this lack of catalytic function, pseudophosphatases have been implicated in various diseases such as Charcot Marie-Tooth disorder, cancer, metabolic disorder, and obesity. Moreover, they have roles in various signaling networks such as spermatogenesis, apoptosis, stress response, tumorigenesis, and neurite differentiation. This review highlights the roles of pseudophosphatases as essential regulators in signaling cascades, providing insight into the function of these catalytically inactive enzymes.

Myopic (HD-PTP, PTPN23) selectively regulates synaptic neuropeptide release

Neurotransmission is mediated by synaptic exocytosis of neuropeptide-containing dense-core vesicles (DCVs) and small-molecule transmitter-containing small synaptic vesicles (SSVs). Exocytosis of both vesicle types depends on Ca²⁺ and shared secretory proteins. Here, we show that increasing or decreasing expression of Myopic (mop, HD-PTP, PTPN23), a Bro1 domain-containing pseudophosphatase implicated in neuronal development and neuropeptide gene expression, increases synaptic neuropeptide stores at the Drosophila neuromuscular junction (NMJ). This occurs without altering DCV content or transport, but synaptic DCV number and age are increased. The effect on synaptic neuropeptide stores is accounted for by inhibition of activity-induced Ca²⁺-dependent neuropeptide release. cAMP-evoked Ca²⁺-independent synaptic neuropeptide release also requires optimal Myopic expression, showing that Myopic affects the DCV secretory machinery shared by cAMP and Ca²⁺ pathways. Presynaptic Myopic is abundant at early endosomes, but interaction with the endosomal sorting complex required for transport III (ESCRT III) protein (CHMP4/Shrub) that mediates Myopic's effect on neuron pruning is not required for control of neuropeptide release. Remarkably, in contrast to the effect on DCVs, Myopic does not affect release from SSVs. Therefore, Myopic selectively regulates synaptic DCV exocytosis that mediates peptidergic transmission at the NMJ.