CEP350 Antibody

What is CEP350 and what is its primary function in cellular biology?

CEP350, also known as Centrosomal Protein 350 kDa or CAP350, functions as a central scaffold protein that coordinates distal-end properties of centrioles. It plays crucial roles in maintaining centriole length, stability, and formation of both distal and subdistal appendages. CEP350 achieves these diverse functions by ensuring centriolar localization of WDR90, recruiting proteins like CEP78 and OFD1 to the distal end of centrioles, and promoting the assembly of subdistal appendages that remove daughter-specific protein Centrobin . The proper functioning of CEP350 is essential for centriole integrity and subsequent centrosome functions, which are critical for cell division and cilium formation.

What is the molecular weight of CEP350 and why might it vary in experimental conditions?

• Post-translational modifications affecting protein migration

• Presence of different isoforms (CEP350 can exist in multiple forms ranging from 65 kDa to 245 kDa)

• Protein conformation affecting migration patterns

• Partial proteolytic processing during sample preparation

When designing experiments to detect CEP350, researchers should be aware of these variations and include appropriate molecular weight markers to correctly identify the protein.

How does CEP350 localization change throughout the cell cycle?

CEP350 exhibits dynamic localization patterns throughout the cell cycle. In G1 cells, both mother and daughter centrioles are decorated with CEP350. During early S phase, when daughter centriole formation begins, CEP350 is only detected on the two mother centrioles while newly forming daughter centrioles lack CEP350 .

As daughter centrioles elongate during S/G2 phase, CEP350 begins to appear on these structures. Initially, a single punctum of CEP350 appears on medium-length daughter centrioles, either on one or both sides. Later, on fully elongated daughter centrioles, the number of CEP350 puncta increases to four . Ultra-Expansion Microscopy (u-ExM) studies have revealed that in mature mother centrioles, CEP350 spans the distal half of the structure in a characteristic dot-like pattern .

How does CEP350 regulate centriole length and stability?

CEP350 regulates centriole length and stability through multiple mechanisms:

First, it contains an N-terminal microtubule binding site (between amino acids 403-725) that contributes to stabilizing centriolar microtubules . Cells lacking CEP350 show increased sensitivity of centriole microtubules to destabilizing agents like nocodazole .

Second, CEP350 recruits key regulatory proteins to the distal end of centrioles that control microtubule length. The CEP350-FOP complex, when associated with either CEP78 or OFD1, plays a crucial role in controlling centriole microtubule length . In CEP350 knockout cells, both OFD1 and CEP78 levels at centrioles are significantly reduced (40% and 15% of control levels, respectively) .

Third, CEP350 maintains proper organization of the centriole inner scaffold. Electron microscopy analysis of CEP350-deficient cells revealed that the inner scaffold remains stable even in elongated regions that lack microtubule triplets, suggesting CEP350 coordinates the relationship between the inner scaffold and centriolar microtubules .

What is the relationship between CEP350 and CEP78 in ciliogenesis?

The relationship between CEP350 and CEP78 represents a critical functional hierarchy in ciliogenesis regulation:

CEP350 promotes the centrosomal recruitment and stability of CEP78 . In CEP350-deficient cells, centriolar levels of CEP78 decrease to approximately 15% compared to control cells . A direct physical interaction occurs between CEP78 and the N-terminal region of CEP350, which is weakened by the disease-associated CEP78 L150S mutation .

Functionally, CEP78 operates downstream of CEP350 to promote ciliogenesis by negatively regulating CP110 levels via an EDD1-dependent mechanism . CEP78 interacts with the EDD1-DYRK2-DDB1-VPRBP E3 ubiquitin ligase complex involved in CP110 ubiquitination and degradation . CP110 is a negative regulator of ciliogenesis, and its proper regulation by the CEP350-CEP78 pathway is essential for cilium formation.

This molecular pathway demonstrates how CEP350 indirectly regulates ciliogenesis by ensuring proper recruitment and stability of CEP78, which subsequently controls CP110 levels through the ubiquitin-proteasome system .

How does CEP350 contribute to centriole appendage formation?

CEP350 plays an essential role in the assembly of both distal and subdistal appendages on centrioles, structures critical for centriole maturation and function:

For distal appendages, CEP350 is required for proper recruitment of CEP164, a key distal appendage protein. In CEP350 knockout cells, CEP164 levels decrease to just 18% of control levels . This dramatic reduction explains why CEP350-deficient cells show defects in distal appendage formation.

For subdistal appendages, CEP350 knockout cells show a 74% reduction in ODF2 levels compared to control cells . ODF2 is a critical component of subdistal appendages, and its significant decrease leads to defective subdistal appendage formation.

Mechanistically, CEP350's role in appendage formation is linked to Centrobin removal. The research shows that subdistal appendage assembly is necessary for the removal of Centrobin from matured centrioles . In CEP350-deficient cells, Centrobin removal is defective - it remains associated with mother centrioles even when they assemble daughter centrioles . This persistence of Centrobin on mother centrioles likely contributes to the defects in appendage formation.

What are the optimal conditions for detecting CEP350 by immunofluorescence?

For optimal detection of CEP350 by immunofluorescence, the following technical parameters should be considered:

Cell types: A431 cells have been validated for CEP350 detection by IF/ICC . When working with other cell types, preliminary validation is advisable.

Fixation methods: While specific fixation conditions for CEP350 are not detailed in the search results, centrosomal proteins are typically best preserved with either cold methanol fixation (-20°C for 10 minutes) or 4% paraformaldehyde followed by permeabilization with 0.1-0.5% Triton X-100.

Imaging considerations: For high-resolution analysis of CEP350 localization patterns, techniques such as ultra-Expansion Microscopy (u-ExM) have been successfully employed . This approach considerably increases resolution beyond conventional microscopy and has been used to reveal CEP350's dot-like pattern on centriole walls.

Controls: Include appropriate centriole markers (e.g., γ-tubulin, centrin) to confirm centrosomal localization, and cell cycle markers if examining dynamic localization patterns of CEP350 throughout the cell cycle.

What are the critical parameters for Western blot detection of CEP350?

Detecting CEP350 by Western blot requires careful optimization due to its high molecular weight and potential isoform variety:

Special considerations include using freshly prepared samples with protease inhibitors to prevent degradation, employing longer transfer times at lower voltage for complete transfer of high molecular weight proteins, and including high-range molecular weight markers to accurately determine the size of CEP350 bands .

Researchers should be aware that while the calculated molecular weight of CEP350 is 351 kDa, it is typically observed at approximately 245 kDa in experimental conditions . Additional bands at lower molecular weights may represent different isoforms or degradation products.

How can I verify the specificity of my CEP350 antibody?

Verifying antibody specificity is crucial for reliable CEP350 detection. Several complementary approaches should be employed:

• Genetic validation: Compare staining patterns between wild-type cells and cells where CEP350 has been depleted by siRNA or CRISPR/Cas9 knockout. A specific antibody should show significantly reduced signal in CEP350-depleted cells .

• Peptide competition: Pre-incubate the antibody with its immunizing peptide before immunostaining or Western blot. This should abolish specific binding if the antibody is truly specific.

• Localization pattern validation: Verify that the observed localization matches established CEP350 patterns. CEP350 should localize to the distal half of centrioles, with dynamic recruitment to daughter centrioles during the cell cycle .

• Multiple antibody validation: Compare results using antibodies raised against different epitopes of CEP350. Consistent results with different antibodies increase confidence in specificity.

• Western blot validation: Confirm that the antibody detects bands of the expected molecular weight (primarily around 245 kDa) in Western blot analyses .

Why might I observe discrepancies between my CEP350 localization data and published results?

Discrepancies in CEP350 localization patterns can arise from several technical and biological factors:

• Cell cycle variation: CEP350 shows dynamic localization throughout the cell cycle. In early S phase, it's only present on mother centrioles, while in late G2 phase, it appears on both mother and daughter centrioles . Differences in cell cycle distribution could explain localization discrepancies.

• Resolution limitations: Standard fluorescence microscopy may not resolve the fine details of CEP350 localization visible with super-resolution techniques. The studies cited in the search results utilized ultra-Expansion Microscopy (u-ExM) to achieve higher resolution imaging of CEP350 .

• Antibody epitope accessibility: Different fixation methods can affect epitope accessibility, particularly for complex structures like centrosomes. Comparing methanol and paraformaldehyde fixation may help identify optimal conditions.

• Dependency on interacting partners: CEP350 localization depends on interactions with proteins like FOP . Variations in expression levels of these partners between experimental systems could affect CEP350 localization patterns.

• Background effects: The p53 status of cells can influence centrosome biology. Note that viable CEP350 knockouts were generated in p53-deficient backgrounds , which might affect centrosome structure and protein localization compared to p53-positive cells.

What phenotypes should I expect when successfully depleting CEP350 in cell culture models?

When CEP350 is successfully depleted, several characteristic phenotypes should be observed that can confirm the effectiveness of your depletion strategy:

• Altered distal-end protein localization: CEP350-deficient cells show significant reductions in several distal end proteins: OFD1 (reduced to 60%), ODF2 (reduced to 26%), and CEP164 (reduced to 18%) compared to control cells. Conversely, C2CD3 levels increase by approximately 78% .

• Centriole elongation: CEP350-deficient centrioles exhibit abnormal elongation, detectable by immunofluorescence as elongated signals of inner scaffold proteins like Centrin and POC5 .

• Defective appendage formation: Both distal and subdistal appendage structures are defective in CEP350-depleted cells .

• Centrobin removal defects: In CEP350-deficient cells, Centrobin remains associated with mother centrioles even when they assemble daughter centrioles, indicating a defect in the Centrobin removal mechanism that normally occurs during centriole maturation .

• Centriolar microtubule destabilization: CEP350-depleted cells show increased sensitivity of centriolar microtubules to destabilizing agents like nocodazole .

• Reduced CEP78 and FOP levels: Centriolar levels of CEP78 and FOP decrease to approximately 15% and 2%, respectively, in CEP350-deficient cells compared to controls .

These phenotypes collectively confirm successful CEP350 depletion and highlight the protein's multiple roles in maintaining centriole structure and function.