Cellular extensions

Cellular extensions
This schematic illustrates the four different types of glial cells, all of which possess cytoplasmic processes: ependymal cells (light pink), astrocytes (green), microglia (red), and oligodendrocytes (light blue). Cell bodies of neurons are in yellow (Their axons are surrounded by myelin, produced by oligodendrocytes).

Cellular extensions also known as cytoplasmic protrusions and cytoplasmic processes are those structures that project from different cells, in the body, or in other organisms. Many of the extensions are cytoplasmic protrusions such as the axon and dendrite of a neuron, known also as cytoplasmic processes.

Different glial cells project cytoplasmic processes. In the brain, the processes of astrocytes form terminal endfeet, foot processes that help to form protective barriers in the brain. In the kidneys specialised cells called podocytes extend processes that terminate in podocyte foot processes that cover capillaries in the nephron. End-processes may also be known as vascular footplates, and in general may exhibit a pyramidal or finger-like morphology.[1][2] Mural cells such as pericytes extend processes to wrap around capillaries.[2]

Foot-like processes are also present in Müller glia (modified astrocytes of the retina),[3] pancreatic stellate cells,[4] dendritic cells,[5] oligodendrocytes,[6] and others. Microglia, which are notably smaller than macroglia, can also extend their end-processes to contact areas of capillaries that are devoid of astrocyte endfeet, and thereby contribute to the formation of the glia limitans.[7]

Other cellular extensions that protrude from the cell membrane are known as membrane protrusions or cell protrusions, also cell appendages, such as flagella, and microvilli.[8][9] Microtentacles are cell protrusions attached to free-floating cells, associated with the spread of some cancer cells.[10]

In prokaryotes such protrusions are known as surface or cell-surface appendages and include flagella, pili, fimbriae, and nanowires.[11][8] Some archaea possess very complex appendages known as hami.[12]

  1. ^ Zhang, XA; Huang, C (September 2012). "Tetraspanins and cell membrane tubular structures". Cellular and Molecular Life Sciences. 69 (17): 2843–52. doi:10.1007/s00018-012-0954-0. PMC 10438980. PMID 22450717.
  2. ^ a b Goddard, LM; Iruela-Arispe, ML (March 2013). "Cellular and molecular regulation of vascular permeability". Thrombosis and Haemostasis. 109 (3): 407–15. doi:10.1160/TH12-09-0678. PMC 3786592. PMID 23389236.
  3. ^ Mescher, Anthony L. (2023). Junqueira's Basic Histology: Text and Atlas (17th ed.). McGraw-Hill Education. ISBN 978-1264930395.
  4. ^ Li, J; Chen, B; Fellows, GF; Goodyer, CG; Wang, R (2021). "Activation of Pancreatic Stellate Cells Is Beneficial for Exocrine but Not Endocrine Cell Differentiation in the Developing Human Pancreas". Frontiers in Cell and Developmental Biology. 9: 694276. doi:10.3389/fcell.2021.694276. PMC 8418189. PMID 34490247. Based on their star ("stellate-like") shape with foot-like processes, PaSCs were found to surround cell clusters, ductal cells and newly formed islets, making complex cell-cell dendritic-like contacts.
  5. ^ Lindquist, JA; Bernhardt, A; Reichardt, C; Sauter, E; Brandt, S; Rana, R; Lindenmeyer, MT; Philipsen, L; Isermann, B; Zhu, C; Mertens, PR (19 May 2023). "Cold Shock Domain Protein DbpA Orchestrates Tubular Cell Damage and Interstitial Fibrosis in Inflammatory Kidney Disease". Cells. 12 (10): 1426. doi:10.3390/cells12101426. PMC 10217384. PMID 37408260. In this context, dendritic cells within the renal interstitium are ideally positioned for immune surveillance, as their foot processes extend into the tubules, allowing them to take up antigens.
  6. ^ Warren, AM; Grossmann, M; Christ-Crain, M; Russell, N (15 September 2023). "Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management". Endocrine Reviews. 44 (5): 819–861. doi:10.1210/endrev/bnad010. PMC 10502587. PMID 36974717. The myelin sheath that protects axons is composed of foot processes of oligodendrocytes, supported by astrocytes that maintain homeostasis and form the blood-brain barrier.
  7. ^ Barkaway, A; Attwell, D; Korte, N (July 2022). "Immune-vascular mural cell interactions: consequences for immune cell trafficking, cerebral blood flow, and the blood-brain barrier". Neurophotonics. 9 (3): 031914. doi:10.1117/1.NPh.9.3.031914. PMC 9107322. PMID 35581998.
  8. ^ a b Orbach, R; Su, X (2020). "Surfing on Membrane Waves: Microvilli, Curved Membranes, and Immune Signaling". Frontiers in Immunology. 11: 2187. doi:10.3389/fimmu.2020.02187. PMC 7516127. PMID 33013920.
  9. ^ "Foundational Model of Anatomy - Cell appendage - Classes | NCBO BioPortal". bioportal.bioontology.org. Retrieved 30 September 2024.
  10. ^ Killilea, AN; Csencsits, R; Le, EBNT; Patel, AM; Kenny, SJ; Xu, K; Downing, KH (15 August 2017). "Cytoskeletal organization in microtentacles". Experimental Cell Research. 357 (2): 291–298. doi:10.1016/j.yexcr.2017.05.024. PMC 5546326. PMID 28551375.
  11. ^ Bouhrour, N; Nibbering, PH; Bendali, F (8 May 2024). "Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens". Pathogens (Basel, Switzerland). 13 (5): 393. doi:10.3390/pathogens13050393. PMC 11124157. PMID 38787246.
  12. ^ Moissl, Christine; Rachel, Reinhard; Briegel, Ariane; Engelhardt, Harald; Huber, Robert (2005-03-07). "The unique structure of archaeal 'hami', highly complex cell appendages with nano-grappling hooks: Unique structure of archaeal 'hami'". Molecular Microbiology. 56 (2): 361–370. doi:10.1111/j.1365-2958.2005.04294.x. PMID 15813730. S2CID 31690026.