Profilin

Profilin

Profilin (blue) in complex with actin (green). (PDB code: 2BTF)
Identifiers
Symbol Profilin
Pfam PF00235
InterPro IPR002097
SMART PROF
PROSITE PS00414
SCOP 2btf
SUPERFAMILY 2btf

Profilin is an actin-binding protein involved in the dynamic turnover and restructuring of the actin cytoskeleton. [1] It is found in all eukaryotic organisms in most cells. Profilin is important for spatially and temporally controlled growth of actin microfilaments, which is an essential process in cellular locomotion and cell shape changes. This restructuring of the actin cytoskeleton is essential for processes such as organ development, wound healing, and the hunting down of infectious intruders by cells of the immune system.

Profilin also binds sequences rich in the amino acid proline in diverse proteins. While most profilin in the cell is bound to actin, profilins have over 50 different binding partners. Many of those are related to actin regulation, but profilin also seems to be involved in activities in the nucleus such as mRNA splicing.[2]

Profilin binds some variants of membrane phospholipids (Phosphatidylinositol (4,5)-bisphosphate and Inositol triphosphate). The function of this interaction is the sequestration of profilin in an "inactive" form, from where it can be released by action of the enzyme phospholipase C.

Profilin is the major allergen present in birch, grass, and other pollen.

Profilin sources and distribution

Profilins are proteins of molecular weights of roughly 14–16 kDa. They are present as single genes in yeast, insects, and worms, and as multiple genes in many other organisms including plants. In mammalian cells, four profilin isoforms have been discovered; profilin-I is expressed in most tissues while profilin-II is predominant in brain and kidney.[3]

Profilin in the regulation of actin dynamics

Profilin enhances actin growth in two ways:

Profilin also negatively regulates PI(3,4)P2 limiting recruitment of lamellipodin to the leading edge of the cell

Profilin is one of the most abundant actin monomer binders, but proteins such as CAP and (in mammals) thymosin β4 have some functional overlaps with profilin. In contrast, ADF/cofilin has some properties that antagonize profilin action.

History of profilin discovery

Profilin was first described by Uno Lindberg and co-workers in the early 1970s as the first actin monomer binding protein.[4] It followed the realization that not only muscle, but also non-muscle cells, contained high concentrations of actin, albeit in part in an unpolymerized form. Profilin was then believed to sequester actin monomers (keep them in a pro-filamentous form), and release them upon a signal to make them accessible for fast actin polymer growth.

Genes

References

  1. Gunning PW, Ghoshdastider U, Whitaker S, Popp D, Robinson RC (2015). "The evolution of compositionally and functionally distinct actin filaments". Journal of Cell Science 128 (11): 2009–19. doi:10.1242/jcs.165563. PMID 25788699.
  2. Di Nardo A, Gareus R, Kwiatkowski D, Witke W (November 2000). "Alternative splicing of the mouse profilin II gene generates functionally different profilin isoforms" (PDF). J. Cell. Sci. 113 (Pt 21): 3795–803. PMID 11034907.
  3. Witke W, Podtelejnikov AV, Di Nardo A, et al. (February 1998). "In mouse brain profilin I and profilin II associate with regulators of the endocytic pathway and actin assembly". EMBO J. 17 (4): 967–76. doi:10.1093/emboj/17.4.967. PMC 1170446. PMID 9463375.
  4. Carlsson L, Nyström LE, Sundkvist I, Markey F, Lindberg U (September 1977). "Actin polymerizability is influenced by profilin, a low molecular weight protein in non-muscle cells". J. Mol. Biol. 115 (3): 465–83. doi:10.1016/0022-2836(77)90166-8. PMID 563468.

Bae YH, Ding Z, Das T, Wells A, Gertler F, Roy P (November 2010). "Profilin1 regulates PI(3,4)P2 and lamellipodin accumulation at the leading edge thus influencing motility of MDA-MB-231 cells". Proc. Natl. Acad. Sci. U.S.A. 107 (50): 21547–21552. doi:10.1073/pnas.1002309107. PMC 3003040. PMID 21115820. 

External links

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