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Megapinosomes and homologous structures in hematopoietic cells.

ABSTRACT: Megapinosomes are endocytic organelles found in human macrophage colony-stimulating factor (M-CSF) monocyte-derived M macrophages. They are large (several microns) and have a complex internal structure that is connected with the cytosol and consists of interconnected knots and concave bridges with sizes in the range of 100 nm. We called this structure trabecular meshwork. The luminal part of the megapinosome can be connected with luminal tubules and cisterns that form the megapinosome complex. The structures are especially well visible in scanning electron tomography when macrophages are prepared by high-pressure freezing and freeze substitution. Our research received a new impulse after studying the literature on hematopoietic cells, where very similar, most likely homologous, structures have been published in peritoneal macrophages as well as in megakaryocytes and blood platelets. In platelets, they serve as membrane storage that is used for structural changes of platelets during activation.

SUBMITTER: Bauer A

PROVIDER: S-EPMC9399034 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Megapinosomes and homologous structures in hematopoietic cells.

Bauer Andrea A Frascaroli Giada G Walther Paul P

Histochemistry and cell biology 20220712 3

Megapinosomes are endocytic organelles found in human macrophage colony-stimulating factor (M-CSF) monocyte-derived M macrophages. They are large (several microns) and have a complex internal structure that is connected with the cytosol and consists of interconnected knots and concave bridges with sizes in the range of 100 nm. We called this structure trabecular meshwork. The luminal part of the megapinosome can be connected with luminal tubules and cisterns that form the megapinosome complex. T ...[more]

PMID: 35829814

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Project description:PALI (release 1.2) contains three-dimensional (3-D) structure-dependent sequence alignments as well as structure-based phylogenetic trees of homologous protein domains in various families. The data set of homologous protein structures has been derived by consulting the SCOP database (release 1.50) and the data set comprises 604 families of homologous proteins involving 2739 protein domain structures with each family made up of at least two members. Each member in a family has been structurally aligned with every other member in the same family (pairwise alignment) and all the members in the family are also aligned using simultaneous super-position (multiple alignment). The structural alignments are performed largely automatically, with manual interventions especially in the cases of distantly related proteins, using the program STAMP (version 4.2). Every family is also associated with two dendrograms, calculated using PHYLIP (version 3.5), one based on a structural dissimilarity metric defined for every pairwise alignment and the other based on similarity of topologically equivalent residues. These dendrograms enable easy comparison of sequence and structure-based relationships among the members in a family. Structure-based alignments with the details of structural and sequence similarities, superposed coordinate sets and dendrograms can be accessed conveniently using a web interface. The database can be queried for protein pairs with sequence or structural similarities falling within a specified range. Thus PALI forms a useful resource to help in analysing the relationship between sequence and structure variation at a given level of sequence similarity. PALI also contains over 653 'orphans' (single member families). Using the web interface involving PSI_BLAST and PHYLIP it is possible to associate the sequence of a new protein with one of the families in PALI and generate a phylogenetic tree combining the query sequence and proteins of known 3-D structure. The database with the web interfaced search and dendrogram generation tools can be accessed at http://pauling.mbu.iisc.ernet. in/ approximately pali.

Dataset Information

Megapinosomes and homologous structures in hematopoietic cells.

Publications

Megapinosomes and homologous structures in hematopoietic cells.

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