Transcription factor EB is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

that in humans is encoded by the ''TFEB''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

Function

TFEB is a master gene for lysosomal

biogenesis Spontaneous generation is a superseded scientific theory that held that living creatures could arise from nonliving matter and that such processes were commonplace and regular. It was hypothesized that certain forms, such as fleas, could arise ...

. It encodes a

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...

that coordinates expression of lysosomal hydrolases, membrane proteins and genes involved in

autophagy Autophagy (or autophagocytosis; from the Ancient Greek , , meaning "self-devouring" and , , meaning "hollow") is the natural, conserved degradation of the cell that removes unnecessary or dysfunctional components through a lysosome-dependent re ...

. Upon nutrient depletion and under aberrant lysosomal storage conditions such as in

lysosomal storage diseases Lysosomal storage diseases (LSDs; ) are a group of over 70 rare inherited metabolic disorders that result from defects in lysosomal function. Lysosomes are sacs of enzymes within cells that digest large molecules and pass the fragments on to other ...

, TFEB translocates from the cytoplasm to the nucleus, resulting in the activation of its target genes. TFEB overexpression in cultured cells induces lysosomal biogenesis, exocytosis and autophagy. In bacterial infection nicotinic acid adenine dinucleotide phosphate (NAADP) induction of lysosomal Ca²⁺ efflux and TFEB activation leads to enhanced expression of inflammatory

cytokine Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in au ...

s. Viral-mediated TFEB overexpression in cellular and mouse models of lysosomal storage disorders and in common neurodegenerative diseases such as Huntington, Parkinson and

Alzheimer Alzheimer's disease (AD) is a neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As t ...

diseases, resulted in intracellular clearance of accumulating molecules and rescue of disease phenotypes. TFEB is activated by PGC1-alpha and promotes reduction of htt aggregation and neurotoxicity in a mouse model of Huntington disease. TFEB overexpression has been found in patients with renal cell carcinoma and pancreatic cancer and was shown to promote tumorogenesis via induction of various oncogenic signals. TFEB constitutive activation, due to FLCN mutations, drives renal cystogenesis and tumorigenesis in

Birt–Hogg–Dubé syndrome Birt–Hogg–Dubé syndrome (BHD), also Hornstein–Birt–Hogg–Dubé syndrome, Hornstein–Knickenberg syndrome, and fibrofolliculomas with trichodiscomas and acrochordons is a human autosomal dominant genetic disorder that can cause suscept ...

. Nuclear localization and activity of TFEB is inhibited by serine phosphorylation by mTORC1 and extracellular signal–regulated kinase 2 ( ERK2). mTORC1 phosphorylation of TFEB occurs at the lysosomal surface, both of which are localized there by interaction with the Rag GTPases. Phosphorylated TFEB is then retained in the cytosol by interaction with

14-3-3 proteins 14-3-3 proteins are a family of conserved regulatory molecules that are expressed in all eukaryotic cells. 14-3-3 proteins have the ability to bind a multitude of functionally diverse signaling proteins, including kinases, phosphatases, and tran ...

. These kinases are tuned to the levels of extracellular nutrients suggesting a coordination in regulation of autophagy and lysosomal biogenesis and partnership of two distinct cellular organelles. Nutrient depletion induces TFEB dephosphorylation and subsequent nuclear translocation via the phosphatase calcineurin. TFEB nuclear export is mediated by CRM1 and is dependent on phosphorylation. TFEB is also a target of the protein kinase AKT/PKB. AKT/PKB phosphorylates TFEB at serine 467 and inhibits TFEB nuclear translocation. Pharmacological inhibition of AKT/PKB activates TFEB, promotes lysosome biogenesis and autophagy, and ameliorates neuropathology in mouse models of Juvenile

Batten disease Batten disease is a fatal disease of the nervous system that typically begins in childhood. Onset of symptoms is usually between 5 and 10 years of age. Often, it is autosomal recessive. It is the common name for a group of disorders called the n ...

and

Sanfilippo syndrome Sanfilippo syndrome, also known as mucopolysaccharidosis type III (MPS III), is a rare autosomal recessive lysosomal storage disease that primarily affects the brain and spinal cord. It is caused by a buildup of large sugar molecules called gly ...

type B. TFEB is activated in

Trex1 Three prime repair exonuclease 1 is an enzyme that in humans is encoded by the ''TREX1'' gene. Function This gene encodes the major 3'->5' DNA exonuclease in human cells. The protein is a non-processive exonuclease that may serve a proofre ...

-deficient cells via inhibition of mTORC1 activity, resulting in an expanded lysosomal compartment.

Function

References

Further reading