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2.A.74.1.3
Lysosomal-associated transmembrane protein 4-beta, LAPTM4B.  Upregulated in many types of cancer cells, in part accounting for multidrug resistance.  Associates with P-Glycoprotein (Li et al. 2010).  May be able to flip lipids from the inner leaflet of the membrane to the outer leaflet, thereby promoting programmed cell death (Blom et al. 2015). This late endosomal protein  controls amino acid transporter interactions (Zhou et al. 2018). The ceramide-mediated regulation of LAPTM4B depends on a sphingolipid interaction motif and an adjacent aspartate residue in the protein's third transmembrane (TMS3) helix. This facilitates the interaction between LAPTM4B and the amino acid transporter heavy chain 4F2hc, thereby controlling mTORC signaling (Zhou et al. 2018). LAPTM4B regulates ceramide-induced exosome release  (Yuyama et al. 2020). (Exosomes are extracellular vesicles that mediate the transport of intracellular molecules, including neurodegenerative agents, and exogenously administrated ceramides, especially those consisting of long fatty acids, accelerate exosome production by neurons and neuroblastoma cells, inducing exosome secretion through LAPTM4B.

Accession Number:Q86VI4
Protein Name:Lysosomal-associated transmembrane protein 4B
Length:370
Molecular Weight:41146.00
Species:Homo sapiens (Human) [9606]
Number of TMSs:4
Location1 / Topology2 / Orientation3: Endomembrane system1 / Multi-pass membrane protein2
Substrate drugs, lipids

Cross database links:

Entrez Gene ID: 55353   
Pfam: PF03821   
KEGG: hsa:55353   

Gene Ontology

GO:0012505 C:endomembrane system
GO:0016021 C:integral to membrane
GO:0006810 P:transport

References (5)

[1] “Molecular cloning and characterization of LAPTM4B, a novel gene upregulated in hepatocellular carcinoma.”  Shao G.-Z.et.al.   12902989
[2] “Signal sequence and keyword trap in silico for selection of full-length human cDNAs encoding secretion or membrane proteins from oligo-capped cDNA libraries.”  Otsuki T.et.al.   16303743
[3] “Towards a catalog of human genes and proteins: sequencing and analysis of 500 novel complete protein coding human cDNAs.”  Wiemann S.et.al.   11230166
[4] “The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).”  The MGC Project Teamet.al.   15489334
[5] “Global survey of phosphotyrosine signaling identifies oncogenic kinases in lung cancer.”  Rikova K.et.al.   18083107

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Predict TMSs (Predict number of transmembrane segments)
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FASTA formatted sequence
1:	MELHERPDER RKARTSTQGR LGDWRRVHAD GFTHRVLGAP AAAWSSSSWL EPAMTSRTRV 
61:	TWPSPPRPLP VPAAAAVAFG AKGTDPAEAR SSRGIEEAGP RAHGRAGREP ERRRSRQQRR 
121:	GGLQARRSTL LKTCARARAT APGAMKMVAP WTRFYSNSCC LCCHVRTGTI LLGVWYLIIN 
181:	AVVLLILLSA LADPDQYNFS SSELGGDFEF MDDANMCIAI AISLLMILIC AMATYGAYKQ 
241:	RAAWIIPFFC YQIFDFALNM LVAITVLIYP NSIQEYIRQL PPNFPYRDDV MSVNPTCLVL 
301:	IILLFISIIL TFKGYLISCV WNCYRYINGR NSSDVLVYVT SNDTTVLLPP YDDATVNGAA 
361:	KEPPPPYVSA