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TRPML1 (or mucolipin 1) is the first member of the TRP family of ion channels that was found to function in the lower portions of the endocytic pathway. Mutations in the gene coding for TRPML1 (MCOLN1) cause the lysosomal storage disease mucolipidosis type IV (MLIV). TRPML1 localization in the lysosomes and the similarity of mucolipidosis type IV phenotype to lysosomal storage diseases whose origin has been directly linked to lysosomal dysfunction, suggest that TRPML1 activity drives some vitally important processes within the endocytic machinery. The specific aspect(s) of TRPML1 activity that make it indispensable for the proper function of the endocytic pathway as well as the specific aspect(s) of the endocytic activity that depend on TRPML1 are currently being discussed. Among the candidates are: membrane fusion within the lower portion of the endocytic pathway possibly mediated by Ca2+ release through TRPML1, or regulation of lysosomal ion homeostasis (pH or Fe content) by TRPML1. In addition to delineating the mechanisms of MLIV pathogenesis, identifying the role of TRPML1 in the endocytic pathway will lead to important developments in our understanding of the endocytic pathway and, due to the neurodegenerative nature of MLIV, of the integrative function of the cell. Moreover, molecular modulators of TRPML1 function may lead to novel approaches to modulating biological processes that depend on the endocytic pathway such as growth factor signaling. The present review will focus on the recent developments in identifying the TRPML1 function. [ABSTRACT FROM AUTHOR]

A million million spermatozoa, All of them alive: Out of their cataclysm but one poor Noah Dare hope to survive. And among that billion minus one Might there have chanced to be Shakespeare, another Newton, a new Donne, But the One was Me. Although biopolymers are more sophisticated than their simpler cousins, such as polythene and rubber, this alone does not give them an obvious reason for existing. Nucleic-acid codes for proteins, some of which contribute to the formation of further nucleic acid, but if these products were free to float away through the surrounding water, no advantage would be gained by the original molecule. The essential extra factor was discovered over 300 years ago. In 1663, using one of the earliest microscopes, Robert Hooke observed that cork has a structure reminiscent of a honeycomb, with pores separated by diaphragms so as to produce a collection of little boxes, which he called cells. Their universality was not appreciated until 1824, when Henri Dutrochet concluded that entire animals and plants are aggregates of cells, arranged according to some definite plan. He also suggested that growth is caused by an increase in either cell size or cell number, or both. The idea of the cell was further elevated in 1838, when Matthias Schleiden proposed that it is the basic structural unit in all organisms. [ABSTRACT FROM AUTHOR]

In Alzheimer's disease, marked activation of the neuronal lysosomal system develops at a very early stage of the disease and intensifies as neurons become evidently compromised. This response, which occurs in virtually all neurons within cell populations susceptible to Alzheimer's disease, is characterized by lysosome proliferation, elevated gene expression and synthesis of lysosmal acid hydrolases, and increased lysosomal protease levels and activities. [ABSTRACT FROM PUBLISHER]

An encyclopedia entry for "sialidoses" is presented. It refers to a group of disorders of lysosomes due to alpha-N-acetyl neuraminidase abnormalities. Among its clinical features are a progressive myclonus epilepsy, bilateral cherry-red spots visible on fundoscopic examination, and enzymatic abnormalities in leukocytes. The entry also presents a description of two phenotypes of sialidoses.

An encyclopedia entry for "ceroid lipofuscinoses (NCL)" is presented. It refers to a group of neurologic disorders which lead in the storage and accumulation of lipopigments in the lysosomes present in the brain and tissues. They are inherited as autosomal recessive conditions and their clinical features are those of progressive myoclonic epilepsy. The classic syndromes in NCL include early infantile, late infantile, juvenile and adult forms. Particular focus is given to the diagnosis of the disease.

A definition of the term "Macrophage" is presented. It refers to a long-lived mononuclear phagocytic cell derived from monocytes in the blood that were produced frmn stem cells in the bone marrow. These cells have a powerful, although nonspecific, role in immune defense. These intensely phagocytic cells contain lysosomes and exert microbicidal action against microbes which they ingest.

A definition of the term "Golgi apparatus" is presented. It refers to a stack of flattened vesicles that functions in posttranslational processing and sorting of proteins. It receives proteins from the endoplasmic reticulum via the endoplasmic reticulum/Golgi intermediate compartment and directs them to endosomes, lysosomes or the plasma membrane.

A definition of the term "lysosome" is presented. It refers to a catabolic organelle in the cytoplasm of eukaryotes. It is characterized by a membrane proto-ATPase that maintains the low pH of 5 to 6. Lysosomes contain hydrolytic enzymes like proteases, nucleases, phosphatases, glucosidases and lipases.