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At least 19 recordsLinked to original sources
PubMed2001

Normal and abnormal secretion by haemopoietic cells.

The secretory lysosomes found in haemopoietic cells provide a very efficient mechanism for delivering the effector proteins of many immune cells in response to antigen recognition. Although secretion shows some similarities to the secretion of specialized granules in other secretory cell types, some aspects of secretory lysosome release appear to be unique to melanocytes and cells of the haemopoietic lineage. Mast cells and platelets have provided excellent models for studying secretion, but recent advances in characterizing the immunological synapse allow a very fine dissection of the secretory process in T lymphocytes. These studies show that secretory lysosomes are secreted from the centre of the talin ring at the synapse. Proper secretion requires a series of Rab and cytoskeletal elements which play critical roles in the specialized secretion of lysosomes in haemopoietic cells.

Blood Cells↗
PubMed2001

Hermansky-Pudlak syndrome and Chediak-Higashi syndrome: disorders of vesicle formation and trafficking.

The rare autosomal recessive metabolic disorders Hermanky-Pudlak syndrome (HPS) and Chediak-Higashi syndrome (CHS)share the clinical findings of oculocutaneous albinism and a platelet storage pool deficiency. In addition, HPS exhibits ceroid lipofuscinosis and CHS is characterized by infections and an accelerated phase. The two disorders result from defects in vesicles of lysosomal lineage. Of the two known HPS-causing genes, HPS1 has no recognizable function, while ADTB3A codes for a subunit of an adaptor complex responsible for new vesicle formation from the trans-Golgi network. Other HPS-causing genes are likely to exist. The only known CHS-causing gene, LYST, codes for a large protein of unknown function. In general, HPS appears to be a disorder of vesicle formation and CHS a defect in vesicle trafficking. These diseases and their variants mirror a group of mouse hypopigmentation mutants. The gene productsinvolved will reveal how the melanosome, platelet dense body, and lysosome are formed and trafficked within cells.

Animals↗
PubMedDate not supplied

Iga nephropathy, antineutrophil cytoplasmic antibodies and crescentic glomerulonephritis in a patient with the Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome is an uncommon cause of renal dysfunction. Because of the risk of bleeding in this condition, few patients have undergone a renal biopsy. Renal dysfunction has been attributed to the deposition of ceroid pigment in the tubules and interstitial fibrosis. We report a case with renal biopsy findings of ceroid deposition and interstitial fibrosis, but also of mesangial IgA deposition, crescentic glomerulonephritis, and an interstitial lymphocytic infiltrate. Furthermore, perinuclear antineutrophil cytoplasmic antibodies of the IgG subclass were detected in a blood sample. It is well known that ceroid pigment in this syndrome accumulates in monocytes, macrophages and T lymphocytes and it has been suggested that this may affect their function. We suggest that this novel combination of renal changes might be explained on the basis of alterations in immune mechanisms in the Hermansky-Pudlak syndrome.

Adult↗
PubMed2001

Cutaneous malignancy in albinism.

Albinism is a disorder of hypopigmentation affecting the skin, appendages, and eyes. Ultraviolet light-induced cutaneous tumors are common in patients with albinism due to reduced or absent protection from melanin. Squamous cell carcinoma (SCC) is the number one skin tumor seen in patients who are albinos. Although nonmelanomatous skin cancers are more common in patients with albinism, dysplastic nevus and melanoma present a greater diagnostic challenge in this group because of their hypopigmented appearance. We report 2 cases of cutaneous malignancies in patients who had oculocutaneous albinism (OCA). The first case involves a 45-year-old man with OCA type 2 (OCA2) who developed a large SCC of the neck. The second case involves a 24-year-old man with Hermansky-Pudiak syndrome (HPS) who developed amelanotic melanoma. In both cases, hypopigmentation of the lesions contributed to a delay in diagnosis. We review the clinical, diagnostic, and therapeutic concerns for patients with albinism who have cutaneous malignancies.

Adult↗
PubMed2001

DNA diagnosis and management of Hermansky-Pudlak syndrome in pregnancy.

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism (OCA), platelet storage pool deficiency, and ceroid lipofuscin deposition. Sequelae including pulmonary fibrosis, colitis, and hemorrhagic diathesis can impact obstetric management. An 18-year-old primigravida with OCA was diagnosed during pregnancy with Hermansky-Pudlak syndrome by DNA analysis. Uneventful vaginal delivery occurred at term following prophylactic platelet transfusion. Women of northwestern Puerto Rican descent with OCA should be offered testing for HPS. Identification of affected individuals may permit optimal obstetric management.

Female↗
PubMed2001

Prenylation of Rab GTPases: molecular mechanisms and involvement in genetic disease.

Small GTPases of the Rab family regulate membrane transport pathways. More than 50 mammalian Rab proteins are known, many with transport step-specific localisation. Rabs must associate with cellular membranes for activity and membrane attachment is mediated by prenyl (geranylgeranyl) post-translational modification. Mutations in genes encoding proteins essential for the geranylgeranylation reaction, Rab escort protein and Rab geranylgeranyl transferase, underlie genetic diseases. Choroideremia patients have loss of function mutations in REP1 and the murine Hermansky-Pudlak syndrome model gunmetal possesses a splice-site mutation in the alpha-subunit of RGGT. Here we discuss recent insights into Rab prenylation and advances towards our understanding of both diseases.

Adaptor Proteins, Signal Transducing↗
PubMedDate not supplied

Hermansky-Pudlak syndrome.

A 55-year-old man had oculocutaneous albinism and a history of frequent bruising following minimal trauma. The simultaneous occurrence of these features was first described by Hermansky and Pudlak in 1959. The Hermansky-Pudlak syndrome follows an autosomal recessive trait and is most frequently found in Puerto Rico and in the Swiss alps. It consists of the triad phenotype of hypopigmentation, prolonged bleeding time due to platelet storage pool deficiency and accumulation of ceroid pigment in lysosomal organelles. Other serious features are pulmonary fibrosis and granulomatous colitis. The disorder is caused by mutations in the HPS1 gene on chromosome 10q23. The HPS1 gene product is involved in the trafficking of melanosomes, platelet dense bodies, and lysosomes.

Diagnosis, Differential↗
PubMed2009

Multipotent genetic suppression of retrotransposon-induced mutations by Nxf1 through fine-tuning of alternative splicing.

Cellular gene expression machinery has coevolved with molecular parasites, such as viruses and transposons, which rely on host cells for their expression and reproduction. We previously reported that a wild-derived allele of mouse Nxf1 (Tap), a key component of the host mRNA nuclear export machinery, suppresses two endogenous retrovirus-induced mutations and shows suggestive evidence of positive selection. Here we show that Nxf1(CAST) suppresses a specific and frequent class of intracisternal A particle (IAP)-induced mutations, including Ap3d1(mh2J), a model for Hermansky-Pudlak syndrome, and Atcay(hes), an orthologous gene model for Cayman ataxia, among others. The molecular phenotype of suppression includes approximately two-fold increase in the level of correctly-spliced mRNA and a decrease in mutant-specific, alternatively-processed RNA accumulating from the inserted allele. Insertional mutations involving ETn and LINE elements are not suppressed, demonstrating a high degree of specificity to this suppression mechanism. These results implicate Nxf1 in some instances of pre-mRNA processing, demonstrate the useful range of Nxf1(CAST) alleles for manipulating existing mouse models of disease, and specifically imply a low functional threshold for therapeutic benefit in Cayman ataxia.

Alternative Splicing↗
PubMed2000

Molecular bases of congenital hypopigmentary disorders in humans and oculocutaneous albinism 1 in Japan.

The molecular bases of various types of congenital hypopigmentary disorders have been clarified in the past 10 years. Homozygous gene mutations of enzymes functional in melanogenesis such as tyrosinase, P protein and DHICA oxidase, result in oculocutaneous albinism (OCA) 1, OCA 2, and OCA 3, respectively. The genes responsible for Hermansky-Pudlak syndrome (HPS) and Chediak-Higashi syndrome (CHS) have also recently been isolated and cloned. The transcription factor paired box 3 (PAX3) works at the promoter region of the microphthalmia-associated transcription factor (MITF) gene, and the MITF transcription factor orders the expression of c-kit, which encodes the receptor for stem-cell factor, which in turn stimulates melanoblast migration from the neural tube to the skin in the embryo. Heterozygous mutations of PAX3, MITF, or c-kit genes induce Waardenburg syndrome (WS) 1/3, WS 2 or Piebaldism, respectively. A defect of endothelin-3 or the endothelin-B receptor produces WS 4. In our examination of 26 OCA 1 patients in Japan, all were found to have homozygous or heterozygous tyrosinase gene mutations at codons 77 or 310. Therefore, mutations at codons 77 and 310 are the major ones in Japanese patients with OCA 1. An autosomal dominant pigmentary disease of dyschromatosis symmetrica hereditaria (DSH) is well known in Japan, and is characterized by a mixture of hypo- and hyper-pigmented macules of various sizes on the backs of the hands and feet. The disease gene and its chromosomal localization have not been identified yet. Our trial of linkage analysis and positional cloning to determine the disease gene is presented.

Albinism, Oculocutaneous↗
PubMed2000

Genomic structure of the mouse Ap3b1 gene in normal and pearl mice.

The mouse hypopigmentation mutant pearl is an established model for Hermansky-Pudlak syndrome (HPS), a genetically heterogenous disease with misregulation of the biogenesis/function of melanosomes, lysosomes, and platelet dense granules. The pearl (Ap3b1) gene encodes the beta3A subunit of the AP-3 adaptor complex, which regulates vesicular trafficking. The genomic structure of the normal Ap3b1 gene includes 25 introns and a putative promoter sequence. The original pearl (pe) mutation, which has an unusually high reversion rate on certain strain backgrounds, has been postulated to be caused by insertion of a transposable element. Indeed, the mutation contains a 215-bp partial mouse transposon at the junction point of a large tandem genomic duplication of 6 exons and associated introns. At the cDNA level, three pearl mutations (pearl, pearl-8J, and pearl-9J) are caused by deletions or duplications of a complete exon(s).

Adaptor Protein Complex alpha Subunits↗
PubMed2001

Rab27a regulates the peripheral distribution of melanosomes in melanocytes.

Rab GTPases are regulators of intracellular membrane traffic. We report a possible function of Rab27a, a protein implicated in several diseases, including Griscelli syndrome, choroideremia, and the Hermansky-Pudlak syndrome mouse model, gunmetal. We studied endogenous Rab27a and overexpressed enhanced GFP-Rab27a fusion protein in several cultured melanocyte and melanoma-derived cell lines. In pigmented cells, we observed that Rab27a decorates melanosomes, whereas in nonpigmented cells Rab27a colocalizes with melanosome-resident proteins. When dominant interfering Rab27a mutants were expressed in pigmented cells, we observed a redistribution of pigment granules with perinuclear clustering. This phenotype is similar to that observed by others in melanocytes derived from the ashen and dilute mutant mice, which bear mutations in the Rab27a and MyoVa loci, respectively. We also found that myosinVa coimmunoprecipitates with Rab27a in extracts from melanocytes and that both Rab27a and myosinVa colocalize on the cytoplasmic face of peripheral melanosomes in wild-type melanocytes. However, the amount of myosinVa in melanosomes from Rab27a-deficient ashen melanocytes is greatly reduced. These results, together with recent data implicating myosinVa in the peripheral capture of melanosomes, suggest that Rab27a is necessary for the recruitment of myosinVa, so allowing the peripheral retention of melanosomes in melanocytes.

Animals↗
PubMed2000

Hermansky-Pudlak syndrome and related disorders of organelle formation.

Hermansky-Pudlak syndrome (HPS) consists of a group of genetically heterogeneous disorders which share the clinical findings of oculocutaneous albinism, a platelet storage pool deficiency, and some degree of ceroid lipofuscinosis. Related diseases share some of these findings and may exhibit other symptoms and signs but the underlying defect in the entire group of disorders involves defective intracellular vesicle formation, transport or fusion. Two HPS-causing genes, HPS1 and ADTB3A, have been isolated but the function of only the latter has been determined. ADTB3A codes for the beta 3A subunit of adaptor complex-3, responsible for vesicle formation from the trans-Golgi network (TGN). The many HPS patients who do not have HPS1 or ADTB3A mutations have their disease because of mutations in other genes. Candidates for these HPS-causing genes include those responsible for mouse models of HPS or for the 'granule' group of eye color genes in Drosophila. Each gene responsible for a subset of HPS or a related disorder codes for a protein which almost certainly plays a pivotal role in vesicular trafficking, inextricably linking clinical and cell biological interests in this group of diseases.

Animals↗
PubMed2000

Abnormal vesicular trafficking in mouse models of Hermansky-Pudlak syndrome.

Hermansky-Pudlak Syndrome (HPS) is a group of related multigenic recessively inherited disorders which causes abnormalities in the biosynthesis and/or function of three related organelles; melanosomes, platelet-dense granules and lysosomes. These lead, in turn, to hypopigmentation, prolonged bleeding and ceroid deposition. Positional cloning strategies have identified five mouse HPS genes. Two orthologous human diseases (HPS1 and HPS2) have likewise been identified. At least four of the five mouse genes encode proteins involved in the regulation of intracellular vesicle trafficking. The pearl (HPS2) and mocha genes encode the beta3A and delta subunits, respectively, of the AP-3 adaptor complex, which captures organelle membrane proteins at the trans-Golgi apparatus. The protein products of the pallid and gunmetal genes are also important components of the vesicular trafficking machinery. The former interacts with a t-SNARE, syntaxin13, and the latter is the alpha subunit of Rab geranylgeranyltransferase, which renders Rab proteins sufficiently lipophilic to function at their target membranes. The pale ear (HPS1) gene encodes a ubiquitously expressed protein of unknown function. Recent physiological studies have shown that mouse HPS mutants, like their human HPS counterparts, have variably reduced lifespans and may have lung abnormalities.

Animals↗
PubMed2000

Defects in the cappuccino (cno) gene on mouse chromosome 5 and human 4p cause Hermansky-Pudlak syndrome by an AP-3-independent mechanism.

Defects in a triad of organelles (melanosomes, platelet granules, and lysosomes) result in albinism, prolonged bleeding, and lysosome abnormalities in Hermansky-Pudlak syndrome (HPS). Defects in HPS1, a protein of unknown function, and in components of the AP-3 complex cause some, but not all, cases of HPS in humans. There have been 15 inherited models of HPS described in the mouse, underscoring its marked genetic heterogeneity. Here we characterize a new spontaneous mutation in the mouse, cappuccino (cno), that maps to mouse chromosome 5 in a region conserved with human 4p15-p16. Melanosomes of cno/cno mice are immature and dramatically decreased in number in the eye and skin, resulting in severe oculocutaneous albinism. Platelet dense body contents (adenosine triphosphate, serotonin) are markedly deficient, leading to defective aggregation and prolonged bleeding. Lysosomal enzyme concentrations are significantly elevated in the kidney and liver. Genetic, immunofluorescence microscopy, and lysosomal protein trafficking studies indicate that the AP-3 complex is intact in cno/cno mice. It was concluded that the cappuccino gene encodes a product involved in an AP-3-independent mechanism critical to the biogenesis of lysosome-related organelles. (Blood. 2000;96:4227-4235)

Adaptor Protein Complex alpha Subunits↗
PubMed2001

Rab27a is required for regulated secretion in cytotoxic T lymphocytes.

Rab27a activity is affected in several mouse models of human disease including Griscelli (ashen mice) and Hermansky-Pudlak (gunmetal mice) syndromes. A loss of function mutation occurs in the Rab27a gene in ashen (ash), whereas in gunmetal (gm) Rab27a dysfunction is secondary to a mutation in the alpha subunit of Rab geranylgeranyl transferase, an enzyme required for prenylation and activation of Rabs. We show here that Rab27a is normally expressed in cytotoxic T lymphocytes (CTLs), but absent in ashen homozygotes (ash/ash). Cytotoxicity and secretion assays show that ash/ash CTLs are unable to kill target cells or to secrete granzyme A and hexosaminidase. By immunofluorescence and electron microscopy, we show polarization but no membrane docking of ash/ash lytic granules at the immunological synapse. In gunmetal CTLs, we show underprenylation and redistribution of Rab27a to the cytosol, implying reduced activity. Gunmetal CTLs show a reduced ability to kill target cells but retain the ability to secrete hexosaminidase and granzyme A. However, only some of the granules polarize to the immunological synapse, and many remain dispersed around the periphery of the CTLs. These results demonstrate that Rab27a is required in a final secretory step and that other Rab proteins also affected in gunmetal are likely to be involved in polarization of the granules to the immunological synapse.

Actin-Related Protein 2↗
PubMed2001

AP-3 mediates tyrosinase but not TRP-1 trafficking in human melanocytes.

Patients with Hermansky-Pudlak syndrome type 2 (HPS-2) have mutations in the beta 3A subunit of adaptor complex-3 (AP-3) and functional deficiency of this complex. AP-3 serves as a coat protein in the formation of new vesicles, including, apparently, the platelet's dense body and the melanocyte's melanosome. We used HPS-2 melanocytes in culture to determine the role of AP-3 in the trafficking of the melanogenic proteins tyrosinase and tyrosinase-related protein-1 (TRP-1). TRP-1 displayed a typical melanosomal pattern in both normal and HPS-2 melanocytes. In contrast, tyrosinase exhibited a melanosomal (i.e., perinuclear and dendritic) pattern in normal cells but only a perinuclear pattern in the HPS-2 melanocytes. In addition, tyrosinase exhibited a normal pattern of expression in HPS-2 melanocytes transfected with a cDNA encoding the beta 3A subunit of the AP-3 complex. This suggests a role for AP-3 in the normal trafficking of tyrosinase to premelanosomes, consistent with the presence of a dileucine recognition signal in the C-terminal portion of the tyrosinase molecule. In the AP-3-deficient cells, tyrosinase was also present in structures resembling late endosomes or multivesicular bodies; these vesicles contained exvaginations devoid of tyrosinase. This suggests that, under normal circumstances, AP-3 may act on multivesicular bodies to form tyrosinase-containing vesicles destined to fuse with premelanosomes. Finally, our studies demonstrate that tyrosinase and TRP-1 use different mechanisms to reach their premelanosomal destination.

Adaptor Proteins, Vesicular Transport↗